GenGAME discusses a few reasons why Steam on Linux (really Ubuntu) is good, how DRM is a necessary evil, and how DRM can cross the line from being necessary to obtrusive in everyday use.
(Battlefield 3, Diablo III, Half-Life 2, Left 4 Dead 2, Linux, PC, Steam)
Ubisoft. That's usually when it gets too far - around the point where the drm nearly requires more memory than the game and let's you play your game only on the fifteenth connection attempt - if at all.