I just had a fantastic idea! Groups!
Maybe someone has had this idea for WP.COM before, I'm not sure, but imagine if you could start groups (or belong to a pool - similarly to how flickr does it).
Essentially it would make for a greater community and a fantastic way to group similar content / interests / people together. I think it's something that could really make this place take off even more.
I think the perfect example is Flickr. Even last.fm has a fantastic groups example. I know livejournal have groups but are they any good?
The way I envisage it working is a "group" has a creator/admin and then they invite users to sign up and approve users to join the group. Then the group page shows the latest posts by all group users (and/or selected/featured group user posts). Pages would be handy and a could also be potentially handy.
A good example of a network of websites that woks well would have to be 9rules.com. Essentially people could create their own blog networks for whatever topic they like (Dogs, Cats, Technology, Gummi Bears, etc).
I know this is a large feature but I cant imagine it being too hard to actually implement. That's why I believe it's possible and great.
What does everyone think?