This is from a thoughtful item by David Weinberger:
I have two premises today. The first is that groups are really, really important. I believe they’re what’s driven the public passion for the Net from the beginning. But I suspect I don’t have to talk you into seeing the value of groups.
Second, the Net is really bad at supporting groups. It’s great for letting groups form, but there are no services built in for helping groups succeed. There’s no agreed-upon structure for representing groups. And if groups are so important, why can’t I even see what groups I’m in? I have no idea what they all are, much less can I manage my participation in them. Each of the groups I’m in is treated as separate from every other.