Avoiding Bayes Poison

[Clay Davis]

Over the past several months I have been saving the spam that slips
through to my users accounts to train my bayes with.  I notice that
lately almost all of it has (what I am assuming to be) an attempt to
poison my bayes (a bunch of valid words put together in a nonsensical
paragraph) at the bottom of it.
 
How much should I worry about this type of spam and how it will affect
my bayes db?  Work arounds?  Advice?
 
Thanks, gang.
 
Clay