As part of the ongoing, rolling personal web site monster, I've been grabbing and consolidating all of my old social bookmarking activity. Spread out over a dozen or so services, it works out to about 1-2 links per day over the course of 20+ years.
What's interesting is looking at the changing patterns of usage over time, and what links have stayed alive. A shocking number of personal blogs have stayed around for decades, for example. Novelty domains, unsurprisingly, vanish quickly.