You guys can debate the ethics of spamming and not spamming all day long. The only way to solve the problem is...
A) Install cloudmark... it's free and it fucking works!
http://www.cloudmark.com Just install it and it will make your life that much easier.
B) Use the delete key on the spam the filter misses.
When you're calculating the time wasted by looking and dealing with spam, be sure to add in the time you guys complain about it on message boards!