I was bidding on a keyword that no one else was and I was getting fantastic results.
I got an email from the advertiser telling me to take down the ad as it violated something.
5 minutes later that advertiser was bidding on the key word that I was just kicked off of.
You can pass the click through your own link first to strip the referrer using php or coldfusion
... and saving the referer information in a file gives you very detailed information about what people really entered in the SE.
Use this information from phrase matching and find new negatives or interesting keyphrases for new direct matches.