it's a "how long is a piece of string" kind of answer I think. but specifically:

I'm working on an approach (nothing public yet) at managing feeds (rss, podcasts, etc), where lists are composable between users. for instance, I follow you, and suppose you had a collection of startup/finance blogs, I'd be interested in transitively folding those into my list of feeds. then, similar to gpodder, feed it out as an opml to synchronize my various places that I consume content. this takes something an early majoritarian already is familiar with, rss feeds, and extends the utility in a way that, at least to me, is compelling.