Valve has announced that game developers can now implement bans on Steam accounts. This is a big deal because enforcing bans was previously a process that Valve did itself, through the Valve Anti-Cheat System.
When a developer finds out a player is cheating, they will notify Valve, which will then issue a game ban on the offending player's Steam account. Game bans will be visible in the player's Steam profile, listing the game they were caught cheating in, like a badge (or many badges) of shame. Valve issued a community post regarding the change, confirming that, well, no one likes cheaters.
Because nobody likes playing with cheaters.
Playing games should be fun. In order to ensure the best possible online multiplayer experience, Valve allows developers to implement their own systems that detect and permanently ban any disruptive players, such as those using cheats.
Game developers inform Valve when a disruptive player has been detected in their game, and Valve applies the game ban to the account. The game developer is solely responsible for the decision to apply a game ban. Valve only enforces the game ban as instructed by the game developer.
For more information about a game ban in a specific game, please contact the developer of that game.
http://www.neoseeker.com/news/26758-steam-bans-can-now-be-issued-by-game-developers-will-be-displayed-on-player-profiles/