Integration as a differentiator doesn't seem to be enough of of a drawn in this context. Friendfeed integrates with other sites that do all of this, and more, as long as they have RSS feeds, and people still use the likes of twitter. With Friendfeed you get to pick which services you want to you use to, say, manage photos, be that flickr, or picassa, or even FF itself.
There must be some advantage to the marketing of these kinds of "add on services" to simple things like twitter that draw people to them; either that or twitter is so stupid simplistic (and they keep removing features) that the market is drawn to add features that the core developers have no interest in maintaining.
