From what i heard i guess its true - A New Pricing Model Rolls Out Today Your Click Charges to be Based on Quality of Traffic you can check this out here - http://www.ysmblog.com/blog/2007/06/04/a-new-pricing-model-rolls-out-today/
Interesting. If they fixed their relevancy, undercut Google, and paid publishers well, they could be in position to take the lead with PPC.