What the previous two answers did not mention is that Steam requires online verification and that it can lock you out from being able to play the games you play

What the previous two answers did not mention is that Steam requires online verification and that it can lock you out from being able to play the games you played for (DRM). See for example: http://en.wikipedia.org/wiki/Steam_(content_delivery)#System_failure http://en.wikipedia.org/wiki/Steam_(content_delivery)#System...