I think the spike you are seeing correlates to the transition from a "field trial" (invite-only) product, to a public product. This is the blog post announcing

I think the spike you are seeing correlates to the transition from a "field trial" (invite-only) product, to a public product. This is the blog post announcing open signups and it is dated September 20th: http://googleblog.blogspot.com/2011/09/google-92-93-94-95-96-97-98-99-100.html http://googleblog.blogspot.com/2011/09/google-92-93-94-95-96...