The convergence of social communication

For how much longer are people going to use separate and disparate social networks, email accounts, instant messenger services and even things like mobile phones - all run by separate providers, each with its own 'friends list' and none compatible with the other?

As it so happens, we are starting to see some convergence:

• GrandCentral already allows you to view and listen to your phone's voicemail from a web page. The technology is promising and has been bought by Google for integration with Google Docs, which includes Google Mail.
• Google Mail and Yahoo Mail already offer a 'lite' chat mechanism from within their web pages, allowing you to chat with your friends who also have Google/Yahoo accounts.
• Facebook now has a mechanism for instigating instant messenger like chats.
• AOL is buying Bebo so that the Bebo social network can be merged with AOL's Instant Messengering (aka AIM) service.

This trend raises some interesting questions, such as 'is convergence useful?' and 'what would a completely converged communication mechanism look/sound/function like?'.