That's what I like about del.icio.us. There are some things is DOESN'T do, but that's because it doesn't have to. It tackles one problem with a few social aspects, and it handles it perfectly.
AdSense for content? What do you mean by that?
It's just been kicking around in my head. Serving targetted 'ads' that link to interesting websites might work considering the numbers of people who go to digg/reddit etc. Arranging it chronologically as everyone does is horrible. I'm sure I've missed a lot on HN because I wasn't here.
But there's a branding problem & I don't see anyone spending months on something that google/stumble/delicious can duplicate with a small script.
Social features may not be worth it if you want the best content. The guy who made delicious purposely didn't include "community" features like ratings or comments. http://simon.incutio.com/notes/2006/summit/schachter.txt
Or from the recent dark knight/godfather episode on IMDB..
"...in these types of situations their cognition or cooperation failed because the members of the crowd were too conscious of the opinions of others and began to emulate each other and conform rather than think differently." - http://news.cnet.com/8301-13515_3-10000650-26.html
Even Dawkins weighed in on this back in 1997 - http://www.simonyi.ox.ac.uk/dawkins/WorldOfDawkins-archive/D...
I think what we need is an adsense for content.