the max is actually pretty high. but when you have a few hundred people making giant tower bases using multiple doors and barricades for each wall to keep people out that maximum limit can get hit pretty quick.
The current max according to a quote from Pat I'm too lazy to dig up is 90,000. That's 90,000 net entities, so if a door is touching another door, it counts it as three. The original system wasn't intended for the masses of shit we're doing to it, thus why Pat did this last wipe and changed the system. Should clear up the problem in the future so instead of your 40 piece fort counting as like, 3000, it'l count as one single entity.