Complain to get free food!
My first email was to a local sit down establishment who had been shorting me on fries with each order, but avoiding them was out of the question as they provide one of my wife's favorite salads. Rather than live with the shortage I email a quick, concise and slightly humorous email to the restaurant's corporate offices, who responded with a $10 gift certificate.
More recently when I stopped at a local Subway to pick up a quick dinner my gift card was refused and then after they decided they could take it, the machine wouldn't process the gift card nor would it take any credit card I had. Since I didn't have enough cash to cover the transaction the employees pitched my food and I had to go up the road to another store in order to get dinner. Again, I wrote a level headed and short email to Subway and a week later I received an apology as well as an explanation of the problem. The manager even sent along a $10 gift card to make up for the problem, which seems to be the token we screwed up amount.
I'm not advocating you to go complaining about every little mix up you encounter, often times these issues can be fixed by the manager on duty. In the event that they can't fix it right then, there's no reason to go spouting off to the Consumerist every time someone making minimum wage at Arby's gives you a made out of roast beef confetti rather than sliced meat. Spend those three minutes writing the company via their corporate website, and almost every time you'll get a great return on your time.When it comes to customer service from corporations the fast food industry is usually quick to make amends as soon as you go above the store level.