Henry,
Users can't delete their Dspam tokens by themselves, but we can do it manually. However, if your filter was already "mature" with a large token database I believe it would take substantial "poisoning" to severely compromise it.
It might be better to continue to work with the token database you have than start again from scratch. Your filter will always adapt to the messages you train it with, so once you stop feeding it the "poisonous" messages it should start improving again.
If you really want us to delete your existing token database we can do that, though.
In Norway we're actually having the warmest November ever since they started recording temperatures 140 (?) years ago. Makes you wonder -- or fear...
- Geir