One thing that just struck me, is that google/gmail will not be banned from workplace computers as often as fb/twitter have been. This alone will be a significant advantage.
Not a great data point, but interesting none the less.
Next thing we could expect is a Farmville in Gmail.
http://www.scansafe.com/content/employers-crack-down-social-...
"76% of companies are choosing to block social networking ... and Webmail (58%)"
Of course, if this thing caught on, presumably more companies would block gmail.