I thought delicious was a killer idea practically from it's launch.
I was pretty surprised when USV invested; it was a bold move, because 2.0 was definitely not hot (possibly getting warm) in the eyes of most VCs at that point. I think this a nice datapoint to show that USV is (relative light-years) ahead of the competition - especially most Silicon Valley investors, who are having a very hard time grappling with investments in the media value chain, and which require deep insight into consumer behaviour.