When you get a tattoo I don't think they care where you have it done as long as you're paying for it, after all the customer is always right 
Not quite. But yes, there may be less professional tattoo parlors where you can probably get whatever you want if you pay (they'll probably be cheaper too).
I think people focus too much on getting the tattoo, and not enough on having the tattoo the rest of their lives.
Precisely!
You're thinking it's 3btc, a little pain, and then it will be over with. But it won't be over. It will be there next year, and 10 years from now, and every year until you die. If it was 3btc to do something once, that would be different. But this is 3btc for a 50-year contract.
Another very good point.
Also what will you do if Bitcoin doesn't succeed, this would be a painful reminder of the failure. On the other side, what if Bitcoin technology changes in the future, and QR codes become obsolete. Than you would have a useless QR code on the back of your neck.
And there's another excellent post...
It would be really silly.
