Showing Displeasure with Really Bad Service

Is it possible to leave a negative tip? Here is one way (not that I would recommend it).
From bitterwaitress.com (Thanks to Jack for the link):

Had a party of 7 so i couldn't add gratuity. They had run me all afternoon and towards the end, a lady asked me for my name. I gave it to her, wondering why, and found out when I realized she left me a personal check for $10.00 as my tip, after paying for the bill with a credit card. I was initially pissed because it wasn't even 10% but I figured what the hell? So I deposited it and forgot about it until three weeks later when I received a letter in the mail from my bank letting me know the check had bounced and because of it, my bank charged me a $7.50 fee.

Total bill / Tip amount / Percentage:
$120.00 / $-7.50 / -6%