Yahoo is Doing some changes in how you use there Services, I don't know about this one.! Looks like many headaches to come..
Call me old fashioned but I don't use Google+ or Facebook to login to other sites.
I believe in signing up with each individual site. You have no idea if a unified login in from say Google will be 100% safe on the other sites end.
Just as of late Yahoo Mail users were notified of not one security breach but two. Why in gods name would you risk the other sites login information to Yahoo.
Yahoo is sliding down the drain. Fast.
I noticed it's kind of difficult to keep up with all different log ins and passwords... due to my aged memory...hopefully the websites don't divulge too much personal private information and respect basic decent privacy...