But in this case, Google is publishing numbers. Numbers that by their own admission aren't even trying to measure the right thing, and which seem to over-count that wrong thing anyways. Given that they're publishing any numbers at all, why are they publishing those numbers in place of more relevant ones?
Well, that's assuming people actually believe what Google. And even they believe what Google says, they don't have any compelling reason to switch from Facebook until their friends actually do switch.
What I mean is that even assuming that people believe google's statement of "it's not a ghost town anymore", they are probably not going to move until it actually stops being a ghost town.