I know many strong players (2000+) that play blitz and they all feel that it is a good way to view many positions and learn openings. While it probably isn't recommended as preparation for a tournament, I don't see how it can destroy your game assuming you stick to the way you play in longer time controls. Personally, I feel blitz is good practice.
One of its faults is hurting your timing (moving too fast in longer time controls), but again, that is another reason why its not recommended tournament practice.
I have recently discovered Live Chess here. I always had rejected that kind of chess games, felt it was a nonsense moving so quick, but now I'm wondering that, apart from the extreme fun you get from those games, whether there is or not some learning values on it. I mean, do you develop some chess skills by playing these way? Or, on the contrary, is it disruptive because you get used to superficial chess and after that you don't analyze in depth positions?
I really don't know what to think about it.