I definitely understand why the public isn't a big fan of his anymore, but I can't help remember back to The Screen Savers, and the early days of digg, when he was really someone I looked up to.
I haven't really been involved in social bookmarking very long, but isn't Digg what spawned the voting-system type site that we see in Reddit and HN? My understanding is that slashdot based on discussion instead of a straight-up voting mechanic.
The difference between Digg and Slashdot is that with Slashdot, all the stories were placed by editors. You might have been able to submit stories to the editors, but there was no upvoting and the front page was purely up to the editors. Of course, later Slashdot added Firehose, and then awhile after that I stopped reading Slashdot.
Slashdot had moderation for comments, but no similar mechanism for stories. Digg had the voting system for stories and for comments.
metafilter predates both Digg and reddit by 5 years, and was enjoyable for quite a while longer than either of them. I don't think it's fair to credit either of those sites with social bookmarking.
I don't know the Reddit history that well, but as I read recently in a PG essay, it was originally slated to be a food ordering application on your phone.
I do not know when they pivoted, or when their idea to pivot came, but I _suspect_ that their pivot was at least partly inspired by Digg's early release.