I second the notion. Read crossing the chasm. What swombat is saying is "find a beachhead, dominate it, then open the platform". Think about facebook and how they dominated one niche then opened it up to everyone else; this model has been used many times successfully for platform companies. The hardest part about this is maintaining focus on the beachhead when you get popular, and saying no to other segments. until you are ready.
Well, they DID start with a niche, say no to the outside, dominate, then use that domination to leapfrog the competition into the mainstream, exactly how crossing the chasm says to. By design or fluke, it was certainly brilliant.
