here is a story at theunderstatement.com about how little the Google Executives and board members have used Google+ in its first three months, from June 28 to October 3, 2011.
http://theunderstatement.com/post/11018308302/googles-management-doesnt-use-google

"Only 3 of the 12 people listed on the Google Management Team page have ever made a single public post on Google+, totaling just 29 posts ever and only 6 in September."

posts from June 28 to October 3, 2011

   7 Larry Page (CEO)
15 Sergey Brin
no account: Eric Schmidt (executive chairman)
150 Vic Gundotra (SVP Social) (his numbers are since mid July)

But the situation is different with Twitter execs...