I have been thinking about this for a while: providing a suppliers review and certification service for small businesses.

Buyers strongly feel this pain, as you can see here:

http://www.sitejabber.com/reviews/www.alibaba.com

In fact, there is a business to be built on this and nobody is executing very well yet. These guys: http://www.tradesparency.com/ have tried, but I think they failed to gain traction. I believe their problems is that you can't simply provide a "yelp for BtoB" as most companies will not be interested in spending time and resources writing reviews on your website. However, there must be other ways to get those reviews...

Any ideas/comments on this?