You've probably read the story by now, but for those of you who missed it: A couple of weeks ago, the site Guru3D tried to do some graphics benchmarking using the Ubisoft game Anno 2070. Every time they changed graphics cards, the DRM required re-activation.
This story spread, and a lot of people made a fuss about it. Once Ubisoft smelled the smoke of bad PR, they engaged in the kind of contradictory activity that only large companies can pull off. They claimed that the DRM was working as intended, which might lead a careful reader to conclude that this unjust punishment of paying customers was deliberate. But then they changed the policy without admitting that their initial policy was wrong, or explaining why they had done things that way in the first case.
As an aside: One of the biggest defenses of online activation-based DRM that the publisher gives us is that legit users can request more activations if they happen to run out. In the case of Guru3D, they did not hear back from support within a day (or more) of asking for more re-activations. In fact, the company said it wasn't going to give them the activations they needed to do their tests. Yes, eventually the policy was changed in response to public outcry, but that's not the same as honoring their initial promise. If that's how Ubisoft will treat a popular website, then what are the odds that you, a lone customer, will get more activations when you need them?
Anyway, back to this story with switching graphics cards...
Some people demanded to know why the DRM ate an install when the customer changed graphics cards. The thinking was, "The DRM shouldn't care when you switch graphics cards, only when you install on a new computer." That's a perfectly reasonable position, although it's not as simple as that in practice.
The problem is that the question of what makes one computer distinct from another computer is a bit metaphysical. When we talk about personal computers, most of us picture a big ol' plastic box that sits under the desk with all of the other computer parts plugged into it. You can gradually upgrade this computer a part at a time over the course of a year. Hard drive, memory, CPU, motherboard, graphics card, operating system, and network card. At the end, you have a totally new computer, but at what point did it stop being the old computer?
Not all of these components have unique identifiers, and it's not always possible / feasible for your DRM program to get at them. You might say that the DRM should trigger an activation if the CPU changes, but CPU's are not unique. If the game locks itself to a particular CPU, then you could dump the game to the hard drive of a different computer with a similar model CPU and it would run without needing activation. It could link itself to a particular install of Windows, but that's nothing more than a simple registry key than can be easily spoofed.