MountainMan: For example, I have no problem whatsoever if a game requires me to have the original CD in the drive in order to play. That is a perfectly reasonable requirement and is in no way burdensome on the consumer.
I thought about the same thing until I bought Crysis. When I tried to play the game it would spin up/down my drive so hard I thought it was going to explode. I immediately went and found a NoDISC exe in order to prevent the drive from being destroyed. It used SecuROM by the way, one of the popular DRM suites that is commonly used for "disc checks".
MountainMan: I absolutely detest protection schemes that secretly install software that could screw with your system or that prevent other legitimate software like CD/DVD imaging tools from working.
Tages and StarForce load drivers that alter the way your optical drives are accessed, and the latter has been accused of forcing the optical drives to run in modes that they don't support, thereby eventually killing them. No clue if that's true or not, but it's certainly a widely held belief. There have been cases where it has interfered with normal operation of recording software, and even SafeDisc complains if it finds blacklisted software on your system. It also is used just for "disc checks".
SecuROM has been accused of using a vulnerable OpenSSL library which opens up security holes in your system, and it has hidden itself pretty well in the past in both the registry and the file system.
I'd say that the majority of cases where a "disc check" is being implemented that it's not an in-house job, and that one of the above mentioned DRM suites are being used.
Just something to think about.