One of Valve’s reasons for introducing the random item unlock system into Team Fortress 2 was that people were doing strange things with the achievement-based unlock system, like joining servers with custom maps made especially for farming achievements. When the new system was released, the problem was that picking up any item was based on time played, thus things got stranger as players soon started going into servers made especially for idling, so began the crusade of players leaving Team Fortress 2 on all night while their account accumulates time therefore increasing the likelihood of receiving an item.
While some players did this the traditional way, which was to simply keep Team Fortress on, some players opted to use external programs to assist in their idling adventures. Valve have announced on the Team Fortress 2 blog that those who did use an external program to idle, which is 4.5% of the playerbase, will have those items removed. But things may not be as rosy in the future, “Due to us not having a policy in place prior to today, this time we’re only removing the items earned through cheating the system. Going forward, if we find users using external applications, we’ll remove all of their items.” Those of us who remained legit will receive one hat free of charge in our inventory. The chances of any other hat finding itself in our inventory have also increased. Valve are also working on a trading system and a method of crafting duplicate items to receive a new item. When will cheaters learn?