Sadly, that's not always the case with Steam - Portal 2's DRM is really annoying. It randomly broke with cryptic error messages or even just silently exited if you tried to run it under Linux using Wine, or used the wrong antivirus software under Windows, or installed it on a FAT filesystem rather than NTFS, or used NTFS symlinks to move the install, or... Apparently the DRM even caused some AMD CPUs to hard-lock: http://forums.steampowered.com/forums/showthread.php?t=25521...