Google has a Hunch
trendslate.com
trendslate.com
Kind of off-topic, but I liked this slide: http://cl.ly/3r1F1l141g2g0T3v3929
It's important to realize that there are different types of chicken and egg problems.
OpenTable, Monster and AdWords don't create a sense of community. There's a strict buyer/seller differentiator between the users.
AirBnB and ebay create something in the middle, where many of the sellers are also buyers (especially in the beginning).
Lastly, sites like etsy and dribbble have a strong sense of community because creators are mostly "selling" to their peers.
An interesting exercise is to take a successful company in one of those columns and bring it to another. In one sense that's what AirBnb did by taking the couchsurfing concept and turning it in to a "hybrid" with a stronger buyer/seller differentiator.
[1] http://blog.okcupid.com/index.php/the-best-questions-for-fir...