Where Are They?
There's lots of discussion in the press about whether Google+ will beat Facebook. To me, this is an irrelevant question. If you look at any historical communication system, there is never an overall winner without a government mandate (and even then, the “winner” is usually not the most profitable). Typically, you get one large player and a lot of smaller players that push interoperability. Unless the big player is larger than all of the small players combined, it is then at a disadvantage.
The question, therefore, is whether Facebook or Google+ will embrace open standards first. Whoever does effectively gets to write the reference implementation and define the baseline for interoperability. This is a market with a huge first-mover advantage. There are lots of competing standards, which is why competition in social networking is in such a poor state. This means that if one of the bigger networks picks a standard and starts pushing it, then it defines the de-facto standard with which everyone else has to interoperate.
Google already did this once, with the Jingle family of standards that are now used for file transfer, voice, and video chat by most XMPP clients.