Louis Gray had a nice post about Subjot yesterday if you are interested in hearing it from someone else's perspective.
http://blog.louisgray.com/2011/08/subjot-subject-based-shari...
It's an ideal concept to sort various different interests of a single person interest into separate containers based on target audience. I think Google+ came close but their naming policy sucks. I wish they'd allow different identity/per-Circle, which could help resolve this issue. But in perspective, I should be able to target my audience based on their interest as I know best and vice-versa. Twitter is totally ineffective here to most degree.