Robert_Charlton - 9:31 am on Jan 19, 2013 (gmt 0)
I would think that Google would like to have people randomly find the listings and not have a large number of them come from direct links.
Might this be mixed to some extent with concern that Google would be suspicious of recommendations that all came from the same IP?... as, eg, a computer set up at the place of business (or a mobile device carried by, say, a plumber) to enable one-time customers to give feedback about their experience.
Justin Sanger (aka "Chicago", one of the founding moderators of this forum), discussed this in his presentation about Google+ at the last PubCon in Las Vegas. I thought it was an extremely important presentation... roughly to the effect that at some point Google might come to accept such customer reviews, particularly if Google+ were involved and the customers were no longer anonymous.
For Google to have meaningful feedback about local businesses that did not have ongoing relationships with customers, he said, some kind of modification in the customer review system was absolutely necessary.