I would say that the ups and downs with YPN is no different than with Adsense. The difference is we are use to make .15 per click with Adsense and when we only make .10 it doesn't seem like a big deal.
With YPN some of us are use to a 4.00 EPC and when it drops to 2.65 we freak out because of the dramatic drop in EPC. In reality the fluctuation between that and Adsense is exactly the same, it just seems more drastic.
