Headshift's Jon Mell has a useful article on How to find the people you need, focusing on those Enterprise 2.0 services that generate most profile information automatically, based on behavior. A lot of this is already possible on the larger web, though it is interesting to note that much of the behavior-based isn't as consistently possible outside the enterprise due to privacy concerns.
Rich profiles can be a powerful cornerstone of an Enterprise 2.0 / next generation intranet / social business software solution. Finding people rather than documents can be highly beneficial in terms of productivity, using information rather than looking for it, and simply getting things done and making things happen.
They are also often misunderstood, many fail to understand that profiles do not require regular maintenance or updating, and can stay current and relevant with very little effort on the profile owner's part. This is a scenario based on Jive Clearspace (although Socialtext and Lotus Connections have very similar functionality) to show how rich, social profiles can help people do their jobs.
Jon provides a nice example scenario here, which sounds like a lot of the demonstrations I have seen of enterprise-level social networking services: jumping from person to topics to documents to other people, based on user behavior in the system, rather than static, manually-entered profiles.
Outside the enterprise, this seems to be more haphazard, though many web sites offer the ability to bring everything together in one place. Since the services are distributed, users must make more manual connections between their profiles and activities in nearly any online service. FriendFeed brings together many feeds in one place, but I don't find the interface terribly compelling. LinkedIn can show recent activity from some resources. Facebook can integrate content from outside services (eBay, Twitter, blog posts, ...), but it cannot come back out. Twitter services provide mechanisms to re-post content into Twitter. Again, however, nearly all of these connections need to be built manually.