It's really amazing (though I guess it shouldn't be surprising) that the saturation there is approaching 100%.

It's because Delicious is something people use to save things, and anything in the form of a list is something that seems like it ought to be kept. You can make any essay seem like a reference work by recasting it as a numbered list.

Delicious/popular was better before writers started intentionally gaming it by doing that sort of thing.