Everyone should do this, now, as a safeguard. If your server is running world edit, and your the administrator/op.

Type in this command:
//limit <number value>

This is going to limit the max world edit block change to 4 million. Now, 2 million is enough to hold a server for about 7 seconds, so depending on your server size you should pick your own.

Desktop servers 1gb of RAM or less: 1,000,000 blocks
Small dedicated servers 15 slots: 2,500,000
Dedicated servers 20 slots: 3,000,000
Large servers 40+slots: 4,000,000
Gigantic servers 80+slots: 5,500,000

A limit higher than 6 million is really not necessary. When are you going to make a 6 million block change.
These general guides should prevent accidental changes from holding your server long enough to kick and disconnect everyone. Your server is going to hold, (lag) But its not going to disconnect you.

Just some info based off of personal experience.