If you're a developer on Steam Greenlight, Valve would like you to consider other forms of marketing than simply giving away game keys. In an announcement to the developer community (the page is locked but was captured in a tweet by Steam Database), Valve told developers that trading game keys to secure votes from players is a bad practice that needs to stop.
"When you give away copies of your game in exchange for votes, you put us in a really uncomfortable position," Valve said. "We do not think these votes accurately reflect customer interest and it makes our job harder in deciding which games customers would actually buy and play on Steam."
Valve continued, noting that developers who do give away game keys are setting a bad precedent and it's not healthy for the Steam ecosystem.
"We understand that running contests or giving away copies of your game can be viewed as a form of marketing," Valve noted. "But for the purposes of Greenlight, we don't think that giving away copies of your game in exchange for votes accurately reflects genuine customer interest."
Valve is asking developers to no longer promise keys for Greenlight votes. pic.twitter.com/8v5zCdEhyl— SteamDB (@SteamDB) February 10, 2015