Online reviews are supposed to be an objective way to get feedback about a product before you buy. However, Amazon's system is often gamed by manufacturers. Cut through the crap with the Verified Purchase filter. As product review site Best Reviews points out, whenever a product lands on Amazon, it has no reviews. This isn't good for the company that made that product, so some will find creative ways to incentivise customers to leave a review. While they can't pay for reviews outright, companies like Snagshout can offer discounts on sample products to users who write "honest reviews". However, as Best Reviews found by examining some reviews, "honest" still tended to be more favourable.
Paid reviews are more likely to get 5-star ratings from Amazon users. Unpaid reviews are more likely to get 1-star ratings. (We determined if a review was paid by looking for the words "honest review" in the writeup, which is what the product distribution agencies require. This is not a perfect filter, but the results are stark enough that we believe it tells the story accurately.)
In fairness, filtering reviews by the phrase "honest review" isn't the most scientific way to measure bias (which Best Reviews openly admits). Fortunately there's an easy way to avoid the problem altogether. Filter your reviews by "Verified Purchase".
Amazon has a special badge for purchases that were made on its site at a price that's close to what a regular customer would expect to pay. These reviews come with a small Verified Purchase badge. This means that Amazon has confirmed the person reviewing it didn't get a free unit and write up an "honest" review. To find it, go to the dedicated reviews page for an item and click the drop down box next to Filter by: to change the option to "Verified purchase only".
That system's not perfect either. Best Reviews found some overlap between the "honest reviews" claim and the verified badge. However, there were very few of them. Moreover, Amazon claims that it's in the process of removing Verified badges from users who purchased items at a steep discount. So, if you want the least biased review you can find, hit that Verified filter. (This is useful even if you don't necessarily intend to buy from Amazon, and are just researching a product.)
Can You Trust Reviews on Amazon? [Best Reviews]