nmservice will give you an error if you remove it or rename it (I recommend renaming it) about every 3 minutes saying "login failed." Some side effects is that you won't be able to see your friends list or guild, and they won't know that you've logged onto the game.
The lack of the nmservice file does not prevent the game from starting, but it does prevent the game from updating/installing (hence I'd still recommend renaming it). Blocking nmservice from the Windows firewall doesn't seem to actually have any effect on it: still logs you into the chat system and as far as I can tell I still have a load of log files.