Some great points have been made which I feel sure we are all digesting however apologies for repeating myself:
I have no reason to doubt these figures therefore why would anyone think/feel/rationale that moving from Adsense to YPN may benefit themselves?
Precisely, and for most "casual" search users this is the problem.
We are all in this forum because we are an expert, or attempting to become one, in search/advertising/publishing/etc.
Joe Public doesn't give a fig about that, they want a relevant answer and, unfortunately, Yahoo's is usually questionable...therefore would you as a publisher use a program which already delivers mediocre results?
At the end of the day for publishers it is the one from which most most money can be earned however for the solo web site owner, it could be make or break!
The real problem Yahoo! have is that Adsense is SO easy to use, as either an advertiser or publisher, that they have to try and replicate it without anyone noticing...others are doing it however I just feel that Yahoo! playing "Follow my leader", just does not ring true.
Apologies for any grammatical errors, it's been a challenging day in the UK.