I was on this morning when the server crashed. Me and a friend had been farming and had moved a ton of stuff inside.
When the server crashed and reset a ton of stuff, all our stuff inside houses did not reset, but all the items that were outside, crops, furnaces, etc all were reset back to some earlier point. It appears houses back up more often than the rest of the world does (or just when someone leaves the house).
We determined that intentionally crashing the server, you would be able to duplicate items by leaving them outside until just before the crash, and then moving them into a house and crashing the server.
Whether this is why the crashes happen or not, it still points to a possible exploit that would lead to hideous consequences for the server.