All my social networks...
It is interesting how things are evolving. We all have many social networks. In the physical world, we readily flip between, or otherwise manage them.
In the physical world, it seems clear we maintain this separation as well as we do because we've had plenty of evolutionary time to work out the procedures -- so much so that they are, for the most part, unconscious. We are aided by physical separation, which is also necessarily integral to the strategies. In the online world, where time and space can, among other things, overlap, the strategies we have for managing our social networks don't apply. In the end, this will call for a re-visioning of the interaction venues, among other things.
In the meantime, to fill in the gap, a number of enterprising startups have appeared. Check out Tumblr and 8hands. I believe they're both addressing the same problem, but from different angles. I can't decide if they're stopgaps, or a permanent part of the new social landscape.