Here's my horror story.
I got mine pierced last February over winter break. I cleaned it twice a day, followed the care instructions, and it healed completely. At prom I was wearing a dangling belly button piercing, one with little stars, which I LOVED! My boyfriend at the time picked me up and the stars wound up getting caught on something.
The piercing didn't rip out completely, but it bled for awhile.
It never fully healed after that. This year at college my friend dowonstairs threw me over his shoulders just fooling around and the stars got caught on his shirt. When he put me down, the piercing stretched the hole even more.
This happened a few more times throughout the year. Finally after a few months without me even realizing, the piercing migrated downward. I had about half a centimeter between the ball of the barbell and my belly button. If I didn't take it out, my body would've continued to reject the piercing and it would've gone right through the skin.
It's already started to close up, but the scar is pretty gross, going the whole length that the piercing migrated. If I had to do it all over again, I never would get it pierced. I seriously look like I have two belly buttons

The worst part is that I took such good care of it, I always cleaned it and didn't change it until the piercer told me to (I went back to the Tattoo shop to have him look at it).
Oh well, my fault I guess. It's a risk you take when you get pierced. The migrating can happen even if you don't get the piercing ripped out, sometimes bodies just reject the piercings.