Even though the question is one of Amazon’s most important features, it’s impressive how understated its introduction was. One day, for many of Amazon’s users (but not all), it just showed up. It was one of many changes occurring on the site that month. Most users didn’t notice it for weeks and few understood how it was going to change the value of the reviews. (It’s not even clear that the team, when they launched it, truly understood what was about to happen.)
Can you guess what the money maker is?
“Was this review helpful to you?”. With those six little words, Amazon saved themselves the cost of an editorial staff while boosting sales by creating a self curated mechanism for pushing the best reviews to the top (and people like reading good reviews). Read the article for the full details, but the way the system works is a great example of good design adding tons of value.