I have several other UbiSoft games that use this very same DRM, but not Assassin's Creed 2. Here's what happens in those other games when I lose internet connectivity.
- The game inexplicably freezes with no error message.
- After several moments (I'd guess about 1 - 2 minutes) a message finally appears on the screen telling me that "UbiSoft's servers have become unreachable".
- After another few seconds, if you still can't contact UbiSoft's servers, the game drops you to your Windows desktop and all unsaved progress to that point is lost.
To be clear, it doesn't have to be YOUR internet connection that fails. It could also be a problem on UbiSoft's end, or anywhere in between. The game only cares about being able to contact UbiSoft's servers, it doesn't care whose fault it is.
To be fair, I've played A LOT of the latest Settlers game and only been kicked out maybe five times. However, much like with the early days of Steam, the first few days of actually owning Settlers 7 I couldn't play it at all, because UbiSoft's DRM servers were under heavy load and wouldn't authenticate my game.
I would not recommend buying a game with this type of DRM, and had I known the games I bought had this DRM, I would not have bought them. I will never buy a game with this type of DRM again.