I guess I don't see the Facebook future quite the same as everybody else.
- SL has a quite extensive FoaF social graph in the transitive closure over everybody's Friends lists.
- FB has currently unrivalled capacity for attaching, augmenting, mining, exposing, and managing social graphs -- to the delight of a half billion or so users.
And nature abhors a vacuum.
Yeah, those Facebook users are "real" people (mostly, kinda), but that doesn't mean the entire social graph is derived from "real" Facebook friends. (It's already demonstrably not; ever gotten a Facebook invitation and noticed who it recommends as friends? Way over the "creepy" threshold.)
I just think the alt account identity problem is the tip of the iceberg, and we're in for a long slog through uncharted territory, with LL's entire business along for the ride. (Which is why I was so bitchy in a comment to Hamlet.)