Can't quite figure out what the heck Wists are for, but they've got tags, buddy lists, and apparently mechanisms for grouping tagged items. Looks like del.icio.us with more spit and polish and some straightforward interface and collaboration extensions.
David Galbraith seems to be the ringleader behind the project. I have to point out though that automatically constructing social networks based on a click will eventually be counterproductive. Tire kicking leads to network management leads to work weeding out stuff every time I just test drive a tie. Blech!
Odd how Wists and Blogmarks, another thumbnail/bookmark combo, surface in the same week. Oh, and what's the over /under on first porn sighting?
Update: Fixed missing angle bracket, so I'm not dissing David Galbraith, who's a fine chap as far as I know.