UPDATE - April 10, 2012

[caigan]

[Chittebengo]

The grinder used didn't so much generate an excessive amount of xp orbs as it did items.

And mobs.

Xp orbs were only once excessive enough to blind me when using a splash potion. We've discussed the situation that lead to problems with responsible individuals. That said, I love the new auto feature.

[Purplecat]

So now with cookies being a currency, what is the ratio between cookies and refined metal?

*hides*

[griffin]

Responsible individual reporting.
I did my best to limit the amount of server resources the grinders generate by stacking all mobs in a 1x1 square - effectively disabling their pathfinding and collision AIs as well as requiring the server to send individual mob positions, as it never changes once they get into that square.

Since the spawns from monster spawners are not mob cap limited, idling in one can end up spawning hundreds of mobs and crash the server. There is however a working failsafe in the zombie/skellie grinder...
You will receive a network timeout before the mob amount gets too high to cause issues for the server - and your disconnect will force all the mobs in the chunk around you to despawn as well.

The problem is that for some reason Blazes do not despawn when the player leaves the area; not sure if that's a feature or a bug. Making blazes despawn-able will prevent further crashes.

Another way would be to implement an idle timeout of say, 30 minutes.