Have one site that does very well with YPN (up to $11 epc). Most traffic comes in through homepage. Took 2 years to get the targeting just right. Very tricky. Two days ago the site went down for 9 hours, and when it came back up, the targeting was completely off even though nothing on the homepage had changed. All other pages have targeted ads, just not the homepage. index1.html, index2.html, etc. will all target but no one sees those pages. index.html will not target no matter what. The four text ads all talk about "staples," i.e. "staples vacations," "staples nursing," "staples pets," etc., which make no sense whatsoever, particularly when there is absolutely NOTHING on our home page that says anything about "staples." This is why YPN makes me crazy.
Adsense does the same thing, have yet to figure it out. I have a few sites that get great targeted ads on all the inner pages, but the index gets weird ads that are not related to the site in any way.