Without some sort of server side authentication, piracy is laughably easy. As far as I know, offline security is basically limited to algorithmic key authentication, which is usually cracked within hours. Google for a key, and you'll find one right there on the first page, without even clicking any links. This is something even the most basic computer user can do, and allows the game to be installed on unlimited machines. The only other protection is disc protection, which can keep multiple copies from being played at the same time (by requiring the disc to be present). That takes slightly more doing to get around, but is no less easy. You don't even have to crack anything. Make a 1:1 copy of the disc, and emulate a drive for the resulting iso.

Given the above, I don't begrudge companies for requiring a one-time online activation. As long as it doesn't inconvenience legitimate users (examples include phoning home all the time, gathering personal info from the local machine, requiring a constant connection, etc) I don't see any problem with it.