That's probably the most annoying problem with the web today. A lot of the people doing web services startups who I talk to are trying to solve some variant of this problem. Personally, I think filtering and visualization together offer the best way to tackle it.
Filtering and visualization are really two sides of the same coin. For instance, once I put the labels on these clusters, it immediately struck me as an excellent way to create friend lists. When you have several hundred friends, manually splitting them into work/family etc. is a daunting task and the vast majority of users never bother. With a nexus-like interface, you could let the user draw freehand curves around the different clusters to use as a starting point for grouping friends into categories. (There is a straight line that almost perfectly separates my college friends from my grad school friends, for example.)
Unfortunately, facebook doesn't allow applications to edit the user's friends list for them, so this feature cannot be implemented for now. I'm thinking of maybe porting nexus to livejournal. Do you think having a tool to create friend lists is a useful feature for lj users?
People apparently hate facebook applications so much that random people in coffee shops who notice me wearing a facebook shirt feel impelled to let me know how they feel about it. I suspect most of these people have never spent five minutes exploring the actually useful applications out there instead of crap like superpoke.