Though I'm still pretty new to news.YC, I think another appropriate and parallel question is this: Does news.YC want to be Digg?
I've seen quite a bit of replication of content across news.YC/Digg/Reddit. Can't we pretty much assume that news.YC readers also peruse Digg and/or Reddit aswell? I do.
No, the right thing to do, clearly, is implement Facebook inside of Digg. Why compromise your own social network by embedding it inside of someone else's site? Especially when you're approximately the same size.