In the hangout from last week on Google+ at the 17:27 minute mark Google's John Mueller said he doesn't think reviews left on your local business has a direct impact on your web search organic rankings. He said "With regards to web search, as far as I know, no. Reviews is not a ranking factor."
The question was:
Is the number of reviews a ranking factor? Assuming all other aspect are the same, would a website with 100 reviews be considered of higher quality then one with only 10 for the same object? If so, how would one implement that value best ? Structured data?
With regards to web search, as far as I know, no. Reviews is not a ranking factor.
It might be different with local but with web search, that’s not a ranking factor.
On the other hand, if these reviews are on your pages than that might be content that we can pick up, that we can show in search, and use as a ranking factor.
Here is the video embed at the start time:
Reviews are great - get them anyway but don't expect them to influence your organic web search rankings.
Forum discussion at Google+.