Well the only reason I'm even bothering with it is to keep the account "active", in case I ever need it, if you know what I mean.
YPN is paying CRAP right now. $0.10/click, with 1/10th the clicks that AdSense gives. You try to contact them and ask what is up, and they give a canned reply.
All PPC industry is not that strong as it used to be.... Payouts are lowered, but some people are paying high $$$ for the clicks for some specific terms.
Your account will still remain active even if you don't use it. I too haven't actually canceled my account (in case a miracle occurs some day when YPN actually becomes a viable program), but don't use it.
YPN IS bad, they are not as good as AdSense If they don't clean up their act, they're bound to go broke.. For me, Kontera is #2 behind Adsense..
I dunno, I keep my Yahoo account on the side, but I don't use it, I only have maybe $25 bucks in there, while Google Adsense is making me a fortune. But in case AdSense ever feels the need to get rid of me, as they have many other people, I'll have a quick backup plan that has a low PayPal payout rate so I can quickly make sure my servers are paid off.