Pretty much basically what these guys said. Fielding more than 50 and cohesion and ability to move quickly diminished. Dunno if these guys have said anything about this or not, but these banes could last for hours upon hours. I remember on Vengeance server, some of those banes went 12+ hours.
I'll post my link to the channel where I've made Shadowbane Videos, some are mine fights and some are banes (sieges) on cities. Hopefully they will help some of the guys that haven't played Shadowbane understand what we love about the game. If i got to Cash's Tree of Life and camp his city for awhile, well that may just result in him dropping a bane on our city.
Also another thing that was usually sure to get yourself baned was crashing someone else banes. Basically an unaffiliated guild would come in and kill both sides as they are fighting each other. Which would usually result in /tells coming from both sides asking why you're helping the other nation out.