I see too many bumps, particularly the Nymwars / privacy issues. My suspicion is that the calculus was to allow more people in as a bid to keep momentum, rather than fix the problems first.
The user experience is going to (or at least should) change very significantly to fix numerous bugs. With more (and less sophisticated) users on board, this will be more problematic.
I'm of two minds about this. As a Nymwar veteran, I naturally see this as a problem. But lots of people don't, especially outside early Internet app adoption groups. Adding scale may make the problem less pronounced by dilution. Privacy seems to be less concerning outside this group as well.
I think this is probably one of the key things they are thinking. Which is it has enough users that they probably have a handle on scaling it and knowing the resources needed per 1000 users, and its fallen off the front page (its not the 'hot ticket' it once was).
I've always found that multiple people editing a document was a killer feature. And with hangouts that seems to make it even better.
The user experience is going to (or at least should) change very significantly to fix numerous bugs. With more (and less sophisticated) users on board, this will be more problematic.