In September 2006, the Pew Research Center conducted a telephone survey which found that 36% of Americans ages 18–25, 40% of those 26-40 and 10% of those 41-64 had a tattoo"

The following is some background information that I chose from Wikipedia. I felt that it was important to include this information to provide some background on the practice of tattooing, as well as history and cultural relevance:

Definition:

"A tattoo is a marking made by inserting indelible ink into the dermis layer of the skin to change the pigment for artistic, ritualistic or other reasons. Tattoos on humans are a type of decorative body modification, while tattoos on animals are most commonly used for identification or branding.

Practice:

Tattooing has been practiced for centuries worldwide. The Ainu, the indigenous people of Japan, traditionally wore facial tattoos. Today one can find Berbers of Tamazgha (North Africa), Māori of New Zealand, Hausa people of Northern Nigeria, Arabic people in East-Turkey and Atayal of Taiwan with facial tattoos. Tattooing was widespread among Polynesian peoples and among certain tribal groups in the Taiwan, Philippines, Borneo, Mentawai Islands, Africa, North America, South America, Mesoamerica, Europe, Japan, Cambodia, New Zealand and Micronesia. Despite some taboos surrounding tattooing, the art continues to be popular in many parts of the world.

Brief historical insight:

Tattooing has been a Eurasian practice at least since around Neolithic times. Ötzi the Iceman, dating from the fourth to fifth millennium BC, was found in the Ötz valley in the Alps and had approximately 57 carbon tattoos consisting of simple dots and lines on his lower spine, behind his left knee, and on his right ankle. These tattoos were thought to be a form of healing because of their placement which resembles acupuncture. Other mummies bearing tattoos and dating from the end of the second millennium BC have been discovered, such as the Mummy of Amunet from Ancient Egypt and the mummies at Pazyryk on theUkok Plateau.

Pre-Christian Germanic, Celtic and other central and northern European tribes were often heavily tattooed, according to surviving accounts. The Picts were famously tattooed (or scarified) with elaborate dark blue woad (or possibly copper for the blue tone) designs. Julius Caesar described these tattoos in Book V of his Gallic Wars (54 BC).

Variois Purposes:

Tattoos have served as rites of passage, marks of status and rank, symbols of religious and spiritual devotion, decorations for bravery, sexual lures and marks of fertility, pledges of love, punishment, amulets and talismans, protection, and as the marks of outcasts, slaves and convicts. The symbolism and impact of tattoos varies in different places and cultures. Tattoos may show how a person feels about a relative (commonly mother/father or daughter/son) or about an unrelated person.

Today, people choose to be tattooed for cosmetic, sentimental/memorial,religious, and magical reasons, and to symbolize their belonging to or identification with particular groups, including criminal gangs (see criminal tattoos) but also a particular ethnic group or law-abiding subculture. Some Māori still choose to wear intricate moko on their faces. In Laos, Cambodia, and Thailand, the yantra tattoo is used for protection against evil and to increase luck. In the Philippines certain tribal groups believe that tattoos have magical qualities, and help to protect their bearers. Most traditional tattooing in the Philippines is related to the bearer's accomplishments in life or rank in the tribe. Among Catholic Croats in Bosnia and Herzegovina, tattoos withChristian symbols would be inked on to protect themselves from the Muslim Turks.

Extensive decorative tattooing is common among members of traditional freak shows and by performance artists who follow in their tradition.

Medical tattoos:

Medical tattoos are used to ensure instruments are properly located for repeated application of radiotherapy and for the areola in some forms of breast reconstruction. Tattooing has also been used to convey medical information about the wearer (e.g. blood group, medical condition, etc). Tattoos are used in skin tones to cover vitiligo, skin pigmentation disorder.

Tattooing in contemporary society:

Tattoos have experienced a resurgence in popularity in many parts of the world, particularly in North and South America, Japan, and Europe. The growth in tattoo culture has seen an influx of new artists into the industry, many of whom have technical and fine arts training. Coupled with advancements in tattoo pigments and the ongoing refinement of the equipment used for tattooing, this has led to an improvement in the quality of tattoos being produced.

^{Logic behind the division in cutlural acceptance of tattoos and tattoo cultures:}

In many traditional cultures tattooing has also enjoyed a resurgence, partially in deference to cultural heritage. Historically, a decline in traditional tribal tattooing in Europe occurred with the spread of Christianity. However, some Christian groups, such as the Knights of St. John of Malta, sported tattoos to show their allegiance. A decline often occurred in other cultures following European efforts to convert aboriginal and indigenous people to Western religious and cultural practices that held tattooing to be a "pagan" or "heathen" activity. Within some traditional indigenous cultures, tattooing takes place within the context of a rite of passage between adolescence and adulthood.

Some stats:

Many studies have been done of the tattooed population and society's view of tattoos. In June 2006 the Journal of the American Academy of Dermatology published the results of a telephone survey which took place in 2004. It found that 36% of Americans ages 18–29, 24% of those 30-40 and 15% of those 41-51 had a tattoo. In September 2006, the Pew Research Center conducted a telephone survey which found that 36% of Americans ages 18–25, 40% of those 26-40 and 10% of those 41-64 had a tattoo. In January 2008, a survey conducted online by Harris Interactive estimated that 14% of all adults in the United States have a tattoo, just slightly down from 2003, when 16% had a tattoo. Among age groups, 9% of those ages 18–24, 32% of those 25-29, 25% of those 30-39 and 12% of those 40-49 have tattoos, as do 8% of those 50-64. Men are just slightly more likely to have a tattoo than women (15% versus 13%).

Christianity:

There is no consistent Christian position on tattooing. The early Christian Montanist movement practiced tattoing as putting signs or seals of God's name according to Rev. 7:3; 9:4; 13:16; 14:1; 20:4; 22:4.

Islam:

Tattoos are considered forbidden in Sunni Islam. According to the book of Sunni traditions, Sahih Bukhari, "The Prophet forbade [...] mutilation (or maiming) of bodies." Sunni Muslims believe tattooing is forbidden and a sin because it involves changing the creation of God (Surah 4 Verse 117-120), and because the Prophet cursed the one who does tattoos and the one for whom that is done. There is, however, difference of scholarly Sunni Muslim opinion as to the reason why tattoos are forbidden. The use of temporary tattoos made with henna is very common and is considered permissible in Muslim North-Africa and other predominantly Muslim nations such as Indonesia and Malaysia.

Jusaism:

Tattoos are forbidden in Judaism based on the Torah (Leviticus 19:28): "You shall not make gashes in your flesh for the dead, or incise any marks on yourselves: I am the Lord." The prohibition is explained by contemporary rabbis as part of a general prohibition on body modification that does not serve a medical purpose (such as to correct a deformity). Maimonides, a leading 12th century scholar of Jewish law and thought, explains the prohibition against tattoos as a Jewish response to paganism. Since it was common practice for ancient pagan worshipers to tattoo themselves with religious iconography and names of gods, Judaism prohibited tattoos entirely in order to disassociate from other religions. In modern times, the association of tattoos with Nazi concentration camps and the Holocaust has given an additional level for revulsion to the practice of tattooing, even among many otherwise fairly secular Jews. It is a common misconception that anyone bearing a tattoo is not permitted to be buried in a Jewish cemetery.

Tattoos can have health risks: 

Because it requires breaking the skin barrier, tattooing may carry health risks, including infection and allergic reactions. Modern tattooists reduce such risks by following universal precautions, working with single-use items, and sterilizing their equipment after each use.

Tattoo removal is an option:

While tattoos are considered permanent, it is sometimes possible to remove them with laser treatments, fully or partially. Typically, black and darker colored inks can be removed more completely. An ink trademarked as InfinitInk is designed to be removed in a single laser treatment. The expense and pain of removing tattoos will typically be greater than the expense and pain of applying them." (This information was taken from Wikipedia)