A lot of what Groupon is generating is demand for something people didn't know they wanted.
The biggest thing is to create a product that consumers find useful. As more and more people like something, it becomes harder and harder to have a conspiracy theory about it.
Where folks like Google have fallen down is in just putting a little review box up, then closing their eyes and letting the algorithm take care of itself. Yelp is a technology company, but also a company that understands how people want to connect with one another.