from ypnblog: To encourage this best practice we have updated our Program Policies, which now require that no more than three ad units appear on a single page at one time. Ament to that!
That should have been their TOS first of all. I guess they tried being a little creedy by allowing their publishers to use unlimited ads and they realised that their Advertisers were not happy about it so they then thought that they would only allow up to 3 ads per page just like their competitor Adsense.
The number of ads on a page should matter none for PPC. Why does it seem so many people are against making money in this world?