Why couldn't an open system allow for different profiles? E.g. personal, professional and public. Facebook has started to get the right idea with its lists feature - but there needs to be far more control - a completely separate profile, option to target statuses to certain groups etc.
Inevitably the solution will be a decentralised social network which other providers can tap into - core functionality such as profiles (and location?) should be as portable as a wordpress blog: either I get someone else to host it or I host it myself.