So I was looking at Crysis on Steam today and I noticed that it had SecuROM with a 5-machine activation limit. Now i know that many people have moral beliefs about whether its right or wrong to have DRM on top of DRM - that's really not what I'm interested in now. What I'd like to know is what the practical, real-world effects of having SecuROM on your system are. I've heard some horror stories about it, and while I know that there were some bad things that happened with Sony and their CD's a while back, most of the stories now adays seem speculative at best with rather little evidence to substantiate the problems (its a rootkit, causes memory problems etc.) 
 
In particular, how does the 5 machine activation limit work on Steam because while I've read about specific deactivations via special tools on the EA and 'manual revocation' from the SecuROM site, I've heard stories of it not working properly with some Steam games, and in addition to that, I don't see Crysis anywhere on that EA page despite Steam saying it has SecuROM.

As long as you deactivate your machine when you uninstall it you should be fine. DRM is a necessary evil these days due to the culture of PC gaming.