In the trade it's called "Fake Review Optimization," the ability to generate positive or negative reviews concerning a hotel online to either generate or discourage traffic through the front door. This blog piece speaks about the phenomenon, which is quite common, and what is being done to stop it.
Not that any of us would ever plant a FRO, right?
I came across such a situation a few months ago using Google serach to look for a company to buy a new furnace from. Something I noticed as suspicious was that a company had perfect reviews almost every day. Thinking that was odd, that everyone that got a furnace installed would put such a stellar review, I started looking at the last few reviewers to see what else they reviewed. The 3 most recent had all bought several new cars from the same dealers, used the same laundry, etc.. Further inspection showed that all did the reviews on different days. Somebody is making money leaving reviews to inflate business reviews, and even being told on what days to make their reviews. Research reviews out there on the web before taking them at face value. Especially when a large purchase is involved!