Valve has commented on Greenlight developers offering free game keys in exchange for vote, posting a message to the developer community.
While that page has since been removed, Steam Database managed to capture a screenshot of the message and post in on Twitter.
"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", the statement reads.
They also comment that giving away free keys like this is unhealthy for the whole system, and that they will take it into account in the future.