In a bid to help bolster trust in its customer ratings, Amazon on Monday announced that it no longer would allow most incentivized reviews -- that is, reviews written in exchange for receiving products free or at a discount. Such reviews comprise only a small percentage of the tens of millions of reviews of products sold on the site, maintained Amazon Vice President of Customer Experience Chee Chew. The company recently introduced a machine learning algorithm that gives more weight to newer, more helpful reviews, he noted.