Isn't this how Steam works? If your account is banned for some reason you lose access to all your games, single-player included. Why is it more of an issue when Bio/EA do it?
There is a
huuuuge difference between a VAC ban and a Steam ban. You have to do a lot of stupid [censored] to get banned from Steam, but hackers and cheaters are VAC banned all the time.
VAC Bans only prevent you from playing the game in question
online on secure servers, you still have access to single player and unsecured servers.
Steam bans do prevent you from playing your Steam games, but those bans are rare and never without reason.
Actually, DA2 requires you to log in once to your EA/Bioware account, to verify your legal purchase. After that, you'll not need to log in at all. But this one time binds the serial to your account, thus locking you out of the game in case you are banned from the game account part of your EA account.
Actually, you never have to log in. You just have to enter your serial key during the installation process. The first time you run the game you see a login menu but you can just press escape to ignore it and play the game. You won't have access to any DLC or online features though.
...or when your purchases are found out (with a fallible mechanism, mind you) to have been not quite legal. Bad credit cards or something like that.
I've never heard of that happening