In parallel to the social side of search, there’s similar stirrings in blog directories.
Kinja users cluster/summarise their blogs & share that summary… easier to see than explain – here’s Kinja’s editors take on food. One step beyond a simple blog directory & search, like technorati.
It’s a natural maturing step. You might even say ‘legitimisation’!
I’d expect these pages to rank well with engines – they’re focussed on one topic, and updated regularly, which should make them a valuable space to advertise, or snag the attention of target interest groups in some other way.