sciencehabit writes "A new study suggests that all the reviews you read on Yelp and Amazon are easily manipulated. It's not that companies are stacking the deck, necessarily, it's that a few positive comments early on can influence future commenters. In fact, when researchers gamed the system on a real news aggregation site, the items received fake positive votes from the researchers were 32% more likely to receive more positive votes compared with a control (abstract). And those comments were no more likely than the control to be down-voted by the next viewer to see them. By the end of the study, positively manipulated comments got an overall boost of about 25%. However, the same did not hold true for negative manipulation. The ratings of comments that got a fake down vote were usually negated by an up vote by the next user to see them."