In this screen shot you can see about 55 players on the screen, but it doesn't include players on the left, right, players inside the bridge, below, etc... there were easily 300-400 players in this battle.

http://puu.sh/7ESQz.jpg

I've seen 4 times as many people in a single charge before, it was scary as hell like a bunch of locusts they came through like wildfire and just took down every keep we had amazingly my PC held up just fine didn't even slow down with 200 people on my screen it's when they drove us back to our keep that I started to see a little slow down. All those siege weapons and crumblings walls seems to be more taxing on the PC than the players were.