"The majority of review score manipulation we're seeing by developers is through the process of giving out Steam keys to their game, which are then used to generate positive reviews," a post on Steam says. "Some developers organize their system using Steam keys on alternate accounts. Some organizations even offer paid services to write positive reviews."
So as a result, Steam reviews stemming from key redemptions won't factor into a game's overall score. Score-affecting reviews will only come from purchases made via Steam itself. "We've now taken action by banning the false reviews and will be ending business relationships with developers that continue violating our rules," the company writes.
All told, Valve says review scores will change for "at least" 160 games (roughly 14 percent) on the service. This isn't a perfect solution, though. As Ars Technica notes, digital versions of Kickstarter games are distributed via Steam keys. That's to say nothing of reputable third-party sellers like Humble Bundle.
As you might expect, many developers are bristling, saying that this will adversely affect their chances of getting noticed on the digital storefront. "We're hearing lots of positive response to this update, and some criticisms," Valve's Doug Lombardi tells Gamasutra. "Like all updates we issue to our games and services, we will be monitoring the community reaction and incorporating that feedback into the next set of changes we make to improve the service for everyone."