I've reformatted several times and haven't done anything in regards to uninstalling or backing up steam and I haven't had any problems reinstalling the game. It's been at least 4 if not 5 times so far.... I wonder how many more I have before it says I can't play?????
On a side note, IMO the # installs limit idea is one of the worst anti-piracy ideas I've ever heard of. The pirates still have no problems at all with the game and those of us that actually paid for it get to deal with a total pain in the ass
If anything, I would think this stupid idea would drive the amount of piracy up instead of down.