Data, no. But I worked at a company that built a product for small business marketing/reputation. So I and my colleagues there spoke to hundreds of different small businesses and it was a recurring theme. My team actually worked on an integration with Yelp, so we had discussions with customers specifically on that topic. At one point, we asked our success team (a team that called customers once per month to proactively help with issues they might be having) to look for customers who were also happy Yelp customers as potential beta testers of our integration. In their first two weeks of calls, they didn't find any happy Yelp customers among the ~18,000 of our customers they called. They eventually found two among the other half of our customer base, but seeing that it was literally 2 out of thousands led me to my point of view.

Of course, it doesn't absolve Google of their tactics. I only mentioned it because it seems like a pot-kettle situation to me. My company actually had its own problems with Google. At one point, Google switched from displaying reviews that we collected and syndicated to them on search results to hiding them behind a "X more reviews on ..." link. I believe it was when Google started collecting their own reviews, but it was before my time there. It almost killed the company and made our offering significantly less valuable.