Call Of Duty: Modern Warfare 2 players have lost the ability to play the game via Steam's Family Sharing feature, just days after release. The feature was switched off in an update deployed yesterday without warning or communication from Activision.
You can spot the change in an update listed on SteamDB.
Steam Family Sharing allows "family members and their guests to play one another's games while earning their own Steam achievements and saving their own game progress to the Steam Cloud." It's a relatively generous system, although there are equivalent processes available for families playing the same game on console, too.
Players are, predictably, not wild about the feature being initially active in Modern Warfare 2 and now removed after they've bought the game.
Modern Warfare 2 is currently one of the most popular games on Steam by concurrent player count, but it has Mixed user reviews as a result of the number of bugs players are encountering. Developers Infinity Ward have created a public Trello board to track known issues and their priority fixes.
We didn't encounter bugs in our time with the campaign, but did find it a mix of the spectacular and the middling in our Call OF Duty: Modern Warfare 2 review.