What is Steam?

[Reverent-One]

Another thing worth noting is that, because it is DRM, you cannot play games you bought on Steam without Steam. You can put it on offline mode, but cannot, say, delete Steam. (No Steam, no games.) Meaning that if Valve ever goes bankrupt, any games you purchased on Steam disappear with it.

Though it should also be noted that the Valve has said measures are in place in the case of such an eventually occurs.