Tattoos I am not that down on. I don't understand the money or time spent in tattooo parlors, but the art itself is art and not uninteresting.
Might get a tat myself, say some Japanese caligraphy on a pect or delt. I'd order some saying by Musashi having to do with swords and wariors and end up with something that said "rice sold here," to the amusement of any Japanese I happened to be soaking in a hot bath with.
Back when I was a tadpole I read about the risk of prison tattoos done with a needle or pin and unsterilized ink. Obvious.
But not long ago I was browsing in a copy of Muscular Development from about 2006 that reported on a study done at UT SW medical center in 2001 on the correlation of tattoos and hepatitis C. Seems those with tats were observed to be six times as likely to have hepatitis C as those without tattoos. If the tats were in color, such as red or white, half of those with tats had hepatitis C.
Wikipedia says there is a 2-3 fold increase in risk. And see http://www.sciencedaily.com/releases/2010/08/100806125506.htm
Makes one worry about one's date, lover, or spouse. Upon meeting a likely prospect for something more, you ask "Have you got any tats?" If the answer is "yes," then you want to hie them to a clinic for some testing before you...ahem...get closer. Maybe you want to hie yourself to the clinic if the deed has already been done.
Obviously, there is a problem with the sterility of tattoo parlors, instruments, and procedures. But there is another explanation that is worrysome too. Those with tattoos are more likely to engage in risky behavior in other ways. To be more sexually promiscuous, to have been in jail or prison, more likely to shoot up with old needles, more likely to shoot up period.
Hepatitis C, btw, is an uncurable virus disease that increases your risk for liver failure, cancer, etc. Basically it significantly reduces your chance for a long and healthy life, but is a step back from AIDS. Like AIDS it is communicated via bodily fluids.