PC Gamer has said that a constant net connection is required to play Assassin's Creed 2 on PC. And if you lose connection with Ubi's servers it kicks you out of your game.
"When we heard of Ubisoft's plan to require an internet connection for all their future PC games, we hoped they'd abort it or scale it back in the face of the outrage and astonishment it caused. They haven't, and it's here," says the PC Gamer blog.
"We've just received Assassin's Creed 2 and Settlers VII for review, and verified with Ubisoft that the DRM is the same as the boxed product. If you get disconnected while playing, you're booted out of the game. All your progress since the last checkpoint or savegame is lost, and your only options are to quit to Windows or wait until you're reconnected."
Read the full blog post here for further details and tell them what you think. Ubisoft will be listening.