Je has already started thinking and working this out, but wouldn’t it be great if you had a ID manager that would allow you to customize your online identities? Not an online “identity manager” but an “online identity” manager (that could be online). Open ID with multiple IDs.
There are more and more social networks popping up for everything. Some you want to have more personal information about you, others not so much. Work related social networks use this group of information, kangaroo clown porn networks use this more anonymous information, for example.
If you could manage all your identities in one place, that would be helpful. It could be online, or a desktop AIR style app.