Valve is now allowing game developers to implement their own systems that can detect and also ban users from playing their games on Steam.
Game Developers Can Now Ban Players from Their Games on Steam
News & Rumors

The new “Game Ban” feature, which aims to ensure that players have the “best possible online multiplayer experience”, was created to reduce the number of “disruptive players” in games sold on Steam.
Games will each have their own different policies and rules that govern how players get banned depending on what conditions the developer sets, which includes but is not limited to people who use cheats.
The system works by allowing developers to create detection systems in their games, that in turn inform Valve of accounts to apply a “Game Ban” to, which may permanently prevent a user from playing that game again. Valve says that the decision to ban players is solely down to the developer and that they are only going to enforce what they have been instructed to do.

Game Bans on Steam
There’s already been some debate on whether this feature could be abused by game developers and questions have been raised on how the system can be trusted.
This feature along with last week’s Steam Account policy update joins Valve’s ongoing effort to crack down on abusive Steam users. Whether this will work, only time will tell.
Just a matter of time until publishers use this to ban people giving games bad reviews or saying “undesireable” things in forums.
Why doesn’t valve just give them the possiblity to edit or delete comments at will?