Just looking over my stats - I think the drop in traffic I'm seeing yesterday is something to do with the "social search" integration.
My traffic dropped on one subdomain significantly yesterday (and dropped slightly on a couple others), but my ranking software shows no change in ranking on hundreds of terms across several subdomains.
So I think they are shoving in more crap into the results from users "social world". In fact, I notice when I search that the stuff that I have +1'd is now higher in ranking then it used to be... that is it used to rank 8 to 10 now it is up to 3-5.
This continues to get worse, because the +1 integrated results aren't even targeted that closely to the search term, just the general topic, and therefore they are off-topic results taking up at least 2-3 spots in the results, starting at position #3.