http://www.vecosys.com/2007/01/28/yahoo ... ts-openid/ (http://www.vecosys.com/2007/01/28/yahoo-supports-openid/)
I've never heard of openID until reading this link. My first thought about having a single sign on to multiple providers of web-based services is that it is a huge security issue. Get someone's openID login, and you gain access to their account in all participating services
My place of employment uses such a thing that is similar to openID. Yes it is a risk, though, imo, the benefits far outweigh the consequences.