I'm one of those people who always whips out a camera when I eat out for possible blogging purposes (besides that I'll forget what I've done if I don't take photos—food-related or not). While my friends are pretty used to it—they sit back when the food arrives until they're sure I've taken all my shots—the other people in the restaurant probably aren't. One part of me thinks, "I hope I'm not annoying other people too much," while the other part thinks, "Oh god, I just need one good shot of this burger...no, that was bad, I need another [moves the burger]...and another [moves the burger]..."
Helena Echlin of CHOW's column Table Manners gives some advice on how to politely take photos of food in restaurants, especially upscale restaurants. It may sound obvious, but doesn't hurt to hear again: Don't use flash, don't move around the table too much, and don't take so many photos that the dish's temperature drastically changes by the time you get to eat it. I see the "no flash" rule broken the most when I eat out; use the highest ISO setting on your camera, use some sort of stabilizer, put a candle in front of your food—or perhaps that dish just isn't meant to be photographed since using flash will make it look bad anyway.
Do you know the rules of polite photo taking? How often do you see other people breaking them?