Panagiotis Stamolampros, a lecturer on business analytics at the Center for Decision Research at the University of Leeds in England, said that research on reviewers is limited, but “what we know for sure is that extroverted and open individuals tend to engage more in social media, and they are also expected to be more involved with online reviews.”

That’s certainly not me. I usually roll my eyes when people in my social network share too much online, and I can’t fathom who would have the extra minutes in the day to write a thoughtful review. And yet I invite people from all over the country to have a say in virtually every aspect of my life.

Stars beget sales. According to an often mentioned Harvard Business School working paper that studied restaurant reviews on Yelp, each added star is associated with a 5 percent to 9 percent increase in revenue. Not surprisingly, then, new businesses have sprung up to exploit the rating system to the seller’s or the platform’s advantage.

In the case of both sellers and platforms, more is more. “Most providers and platforms just want to encourage more reviews,” said June Cotte, a professor of marketing at Western University in Canada. “More reviews signal quality, and it also mutes any bad reviews.”

The tactics to make this happen often lead to rendering the star-rating scale useless. I’m not even talking about asking friends or relatives or paying firms to crank out five-star reviews. (The Federal Trade Commission is cracking down on dishonest practices, while some platforms, like Yelp and Amazon, have designed automated software to combat this, albeit to varying degrees of success.) I’m referring to usually perfectly legit methods, like asking loyal customers to write reviews.

Even if businesses don’t interfere at all, a five-star filter’s usefulness could eventually fizzle out anyway. That’s because in the star-rated universe, the wisdom of the crowd can morph into something more like “the madness of the crowd,” said Matthew Salganik, the author of “Bit by Bit: Social Research in the Digital Age” and a professor of sociology at Princeton.

“Knowing more about what other people are doing and thinking can help us all find the best things faster, but it can also lead to stronger fads where people are following people who are following people who are following people,” he said. “At a certain point, popularity can become separated from how good something actually is.”