Check out AdFreak.com on how Virgin Mobile has found its niche. An excerpt:
In Mother New York's new campaign, "The Crazy Life," Virgin Mobile seems to be staking its claim as the cellular service for the mentally imbalanced. Well, I suppose Droid cornered the market on sci-fi geeks, and Apple has a lock on self-centered hipsters, so there weren't many niches left. The insane need cellphones too, mainly to talk to themselves.