I had 60+ games installed on my harddrive, between XBLA and installed games. When I got home from work last night and turned on the console I only had 27. I was checking for the missing games, and some of them were disc games I had installed, some were XBLA games. From what I can tell no saved data was deleted. When I went into the game marketplace to check the games that were missing they showed I had downloaded them. And I could redownload them again without cost.
Any idea on how or why these games suddenly disappeared?