People are used to having a Facebook id. They go there to hang out with their friends or their old buddies. They're not used to needing to log in to search google, and I doubt they are going to want to. Google is increasingly making you need to have a google account to do stuff, but I find that it is making me use the services less and less. For instance, I use youtube less now.

Google+ may well be successful, but having learned my lesson with Facebook, I'm going the other way. I'm slowly shutting down all my gmail accounts and migrating it to my own domains and servers. My app engine app is going away, and my google apps accounts have migrated. Google docs etc, have been replaced with another solution.

Eventually, and pretty soon, I'll have no more google accounts.