Yelp is an awesome service, but I am surprised to see that they are still not profitable. Considering an annual revenue run rate of approx. $70m, I am wondering what costs them $70m a year to run the site - with most online businesses salaries and marketing are the biggest expenses and considering Yelp's amazing organic rankings, I doubt they are buying a lot of traffic. Any idea what the other big costs are? Sales teams, perhaps?
I doubt they would pay people to review, unless it's a well kept secret. What they do have are Community Managers. They are located in each major city prompting Yelp, providing support for the yelpers in that city and so on. They probably spend a lot on their sales team as well.
I highly doubt Yelp pays people to review...anymore. They did when they first launched (they've admitted to this), but with their brand recognition now, paying people to review would be a giant waste of money. That being said, they haven't reached profitability yet, so who knows, maybe they are making this bad decision.
