Diablo III, let's go back one iteration to a game that's actually available. Blizzard has released patch 1.12 for Diablo II, which allows you to run the full game without the disc in the tray, provided you have all the required .MPQ files. According to BlizzPlanet, that either requires a full re-installation or copy-and-pasting the proper files onto the computer.
The patch also fixes some compatibility with Intel Macs and resets the online rankings. Our friends at BigDownload speculate this might be preliminary steps to putting the game on Blizzard's digital download store. Blizzard, known for patching games years after their release, updated Starcraft as recently as 2007.