Google may no longer allow SMBs to run client contests for money or charity to gather reviews. That doesn’t slow Google down from encouraging G+ Local users from leaving more reviews by digging into a users search history.
The Google Plus Daily noted several days ago that Google+ Local Now Suggests Places to Review. Google is using your search history and checkins to inform the nag.
Clearly Google is exploring one more way to “close the search to sale loop” and determine when a searcher actually makes a purchase. When you combine this with Offers, Check-Ins, Driving Dirctions, Wallet, Zavers (Coupons), various iPhone apps and the use of Android, Google is clearly going to triangulate their way to conversion information if they can’t get it directly and they are obviously looking across all of their software to find it.