Too many social networks. Too many social bookmarking services.
Social networks haven’t been around all that long, but already they have some negative associations. Social networks are black holes for sucking time, or, do I really need one more social network to add my information to and try to maintain? But just because the word ‘Social’ is in the same breadth as bookmarking, doesn’t mean that using a social bookmarking service is anything like your Facebook’s and your MySpace’s.
There are a lot of choices for sharing links out there, Delicious, Magnolia, Diigo, Furl, Blinklist and many other options and variations. I started out using Delicious, and briefly used Blinklist. But Diigo blows every competitor out of the water because it is more robust and built will groups in mind.