If you ever regret getting a tattoo and want to get it removed via laser, here's some research that Italian dermatologists have done on the subject: a little less than half of the tattoos can be fully removed with 10 laser treatments. If you get 15 treatments, you can remove up to 75% of them.
Interestingly, though, they've found that people who smoke have 70% less chance of getting the tattoo removed in 10 treatments. Here's some other factors to keep in mind about this: Tattoos that are red or black come off easier. Black is the easiest. Tattoos on feet or legs are harder to remove than in other places.