I know that guys using Adsense are seeing 25% - 75% CTR's (some higher) on their arbitrage pages that they are sending traffic to. I figure due to YPN's poor ad targetting it will be considerably less with them. What have you seen or experienced?
I think that if you get 25% CTR or over then Google or Yahoo will look more closely at your site to see how you are earning this amount. If your site looks like it is made for adsense or YPN, then you may get banned.