Fallout: New Vegas for the PC will use Steamworks for its digital rights management, according to publisher Bethesda. According to Bethesda's Jason Bergman, Fallout: New Vegas is using Steamworks as its DRM solution because it provides a number of benefits including achievements, friends list support, and other features. Of course this means users will have to have the Steam client installed in order to play the game. There are worse methods for providing DRM like "always on."
While you will have to be online when you first install it, there aren't too many other restrictions you have to worry about. Users can install the game on as many machines as they want and after that first initial install you won't need the disc again; you can download it directly from Steam after that.
New Vegas is being developed by Obsidian Entertainment under the watchful eye of Bethesda Softworks and will be out this fall for PC, Xbox 360 and PS3.