Steve Goodwin recently postulated the idea of a Wistow Number which I've decided, for purposes of paranoia, to take as a compliment.
Weirdly enough this was the original reason I bought (or had bought for me, technically) thegestalt.org several years ago since some friends and I had joked about a roughly similar concept and I had visions of creating a giant graph of a large swathe of the London Geek community.
I started a prototype which needed facilities to delete and edit nodes (or entities) and also for entities and nodes to have timespans (with a possibly open 'end' date).
The nifty part, as far as I'm concerned, was that it not round the scaling problems of, say, FOAF because it only allowed connections between people in very specific cases such as them being blood relations, them being in a relationship and them changing their name. To be honest I was a bit iffy about the relationship thing as well.
I'm not sure why I never finished it - probably the same problems I always have in that I get disheartened when trying to dot the Is, cross the Ts and do the general spit and polish that makes a good app great. Oh for a pet designer.