Ubisoft's new DRM system in Assassins Creed 2 requires you to be online all the time. If you lose your internet connection then the game stops, your lose your current progress and it won't work until it can reconnect. All your save games are kept on their servers as well.

What genius came up with this system? All it is going to do is aggravate people. The limited activation system used in other games is bad enough but at least they don't require a constant internet connection.