Oh hi.
http://www.pawngame.com/
(That's cool)
Oh, I'm not saying it's impossible for Flash games in general to be online, but in N's case,
it isn't designed for it, so it will not work, like you said. Instead they focused on creating some of the best single-player action currently available anywhere from what I've seen, and besides, you can pretty much use the forums and IRC to share demos of maps on NUMA, hold map-making or gameplay competitions with other members, among many other things, which shows the pure amount of amazingness the game really is. Also:
1) N was created by 2 people with limited money in 2004, with the entire gameplay not made for multiplayer either, so implementing it in a finctional or fun way is beyond me, (Again, I don't know how N+ will turn out) and it has progressed to an amazing point now. I understand Pawn wasn't exactly created by a huge company either, but they obviously have a good amount of resources available for this.
2) The game is hosted on CrazyMonkeyGames servers, and this once again goes back to point 1: they must have resources M&R (Mare and Raigan) do not.
3) If you haven't already, please check out the
Wiki and the forums for community information and all the features N has to offer.