No you need it for Windows Live registration - and unless you really need the Achievements etc. Windows Live is a totally optional and entirely unnecessary part of playing FO3. I've never got Windows Live to work properly on my PC, and it hasn't affected the game one little bit. Maybe if there was still DLC out there, but with GotY, you get all the DLC so it's not an issue.
In fact you don't even need the CD to play FO3, if you create a shortcut directly to the game (fallout.exe) rather than the launcher (which is what is created by default when you install).
DA: Origins: maybe the worst love scenes ever in VG history?!