Oh, and just recount the bumps when a post is deleted. So let's say your threads were layed out like so:

Thread 1.
Thread 2.
Thread 3.
Thread 4.
Thread 5.

Thread 5 is bumped and is now Thread 1. The post that bumped Thread 5 is deleted. Thread 1 returns to Thread 5. This is basically "reverse bumping"

Make it an opt-out feature. It should be the default to prevent spam, imo.

To OdiliTime: Thoughts?