Over the weekend, Chris Whiteside, Lead Producer at Guild Wars 2 developers ArenaNet, took to Reddit to announce that over 3000 players had been temporarily banned from the game for taking advantage of an exploit.
The exploit in question involved a merchant who, in an error, was selling valuable gear at low, incorrect prices. Taking advantage of this, many players bought a ton of stuff from the seller, then went elsewhere in the game to sell it for massive profits, which had the temporary effect of upsetting the game's economy.
"We take our community and the integrity of the game very seriously, and want to be clear that intentionally exploiting the game is unacceptable", Whiteside wrote. "The players we banned were certainly intentionally and repeatedly exploiting a bug in the game. We intended to send a very clear message that exploiting the game in this way will not be tolerated, and we believe this message now has been well understood."
The bans aren't permanent, with those caught only being cut off the game for 72 hours. Regardless, any type of punishment for those taking advantage of an exploit in a game can be a controversial move, as those caught were still, technically, acting within the rules of the game. They didn't hack the game to get low prices, they simply bought and sold according to the prices present in the game at the time.
Still, as ArenaNet and others will counter, exploits like this violate the spirit of the game. And at the end of the day, it's ArenaNet's game, and they'll police it how they want, protests be damned.