Industry term: Social Bookmarking
Basically a way for others to bookmark and share what they think is cool with others. The more people bookmark the same thing, the more prominently it's displayed in category listings, tag searches, etc.
Upsides: Power to the people!
Downsides: Feedback loops (the more popular something is the more it's bookmarked, and thus the more popular it becomes, in turn burying other items that could potentially be more relevant), disproportionate representation to minority of users who are highly active bookmarkers (techies for example bookmarking tech news, linux tips, etc).
Personally I use Furl - actually caches a copy of the pages you bookmark so even if the page disappears you can still view it.
--Illah