Anyone know of any user-generated content sites with quality design?

There seems to be a huge gap between a typical SAAS and a user generated content site when it comes to design. The former being much better.

SAAS: Heroku, MailChimp, Vimeo, Dropbox, Indinero

User Generated Content: Reddit, HN, Ebay, Craigslist, Forums in general, ect.

TLDR: Anyone have any examples of sites that are based on user generated content AND have top-notch design. Or any info on designing with dynamic content.

I guess Fourquare/Digg qualify.