Evil is forcing a creature into eternal servitude by sealing him into hosts aka the Jincuriki. I'm with darth on this one, for all we know, all the tailed beasts really want is a chance to show the world that they can dance like ballerinas.
yea, I'd go mental too if i'd been locked up inside a succession of kids for generations.
all i'm saying is that actually we know so little about what really drives the tailed beasts, perhaps they may even WANT to get reunited into the 10 tails ?!?!