A hot topic recently are the viral like DRM protections software houses insert into games. Ubisoft has confirmed that the PC its open-world shooter Far Cry 2, will use a slightly different configuration of the SecuROM DRM technology found in Spore and Crysis Warhead.
You have 5 activations on 3 separate PCs.
Uninstalling the game "refunds" an activation. This process is called "revoke", so as long as you complete proper uninstall you will be able to install the game an unlimited number of times on 3 systems.
You can upgrade your computer as many time as you want (using our revoke system)
Ubisoft is committed to the support of our games, and additional activations can be provided.
Ubisoft is committed to the long term support of our games: you'll always be able to play Far Cry 2.
Overall, I think this is a reasonably fair compromize. Not great, but definitely the gamers can work with and get used to.