More specifically: skype-profitable, but hemorrhaging money for ebay, ebay $1B in the hole facebook-not profitable, needs new investment youtube - not profitable, hemorrhaging money for google digg - not profitable, can't find a buyer reddit- acquired for a pittance, can't find advertisers delicious- don't know

See a pattern here? Other than the big search engines, I can't think of very many startups that are cash flow positive. Unless you're selling something or licensing, simple mathematics will tell you it's very hard to make millions from ad revenue alone.