When someone blames their failure on their technology, I'm always highly skeptical. Good developers and good management (equivalently: good strategy and good execution) could use Cobol and still beat super-advanced alien technology if it's being run by a pack of monkeys. I'm not going to comment on whether .NET is a good choice or not, but even if it was not as good as alternatives, I strongly doubt that MySpace would have beaten Facebook if only it were on a different platform.