If you write a review on TripAdvisor they will let you know. This review was written by a HelpHound staffer exactly a week ago:
Today they received an email from TripAdvisor that contained this:
52 readers in a week - do you think that helped the restaurant?
At HelpHound we operate a slightly different system. We allow readers to vote a review 'helpful' and then we publish the votes. Here's an example for an estate agent client:
Click to expand
You can see the number of helpful votes at the bottom. And we reckon that a review has perhaps 10 readers per helpful vote.
So we think we've answered our question - reviews are read and news does travel - quickly.