Working Around The Spam Filter

Seth Godin posted about his gmail spam filter
blocking orders from Google.

Is this surprising?
No.
All of my email accounts block legit messages.
One even blocks emails
from addresses in my address book.

Does this mean the spam filter is useless?
Another no.
I read each message reaching my inbox.
I scan each message heading and email address in my trash.
It still saves time.

What are you missing out on
thanks to your spam filter?