OpenID & Auto Logins

I've seen many a web site offer to allow me to log in using one of my other logins (usually through a social website like Facebook or Google,) however this is not something I would want to do all the time. It isn't that it's insecure, it's the fact that these Social websites often tend to fall into obscurity after awhile. I mean afterall, do you check your MySpace account anymore, or are you too busy on Facebook these days? If you have a login to a service or site like, for example, Pandora; using your Facebook login, well let's say years from now FB is no more, then what happens to that login to Pandora? Does it just go away? well, my guess is that Pandora will give you the chance to keep your account by asking you to create a username and password. But, why not get into that practice right now? I like the idea of the OpenID system but I think I am more than capable of managing my own login credentials. What do you think?