I have a tattoo that go's from the top of my shoulder down to my elbow. One of the main reasons i got it when i did was because they were fashionable at the time, it's a tribal design.
This is a very silly reason to have one, and a lot of thought should be had before actually having any work done.
I got lucky, a member of my family is a tattoo artist and he did the pattern on my arm 'on the fly', so i know i'm the only person in the world to have it. And i don't regret having it at all, as i still really like it. But i could very easily regret having it due to the reasons i had it.
I will be having more though, i'm getting married this year and i will be having some work done to commemorate that.