Steam Library Backup - do you do it?

Just curious - I used to backup some of my games but they take up so much space these days I'm tempted to just say, "Screw it."

There's always a possibility of Valve/Steam going bye bye... but I dunno if I can be bothered to spend the time and money to do this.

cheshirecatgirl makes a good point - backing up can save you time when reinstalling OS/get new computer {crap - can't edit polls lol}

PS: Do games with limited installs DRM count backup restores as a seperate install (I'm guessing yes)

PPS: theemu linked a discussion involving this topic that Steam has addressed before