A food blog I read, ReMARKable Palate, had a recent article on the safety of tea. The author, a chef, and thus someone who has to take periodic food-safety classes, asserted that sun tea can be dangerous. Sun tea just involves putting a bunch of tea bags in water in a big glass jar, and letting it sit out in the sun for an afternoon. Food safety people worry that bacteria on the tea (or in the water, or on the jug) could grow in the warm conditions of the jar and cause illness. Fair enough, I suppose, except that the evidence that this happens often is very very sketchy. Some Google searches shows that there a couple of suspected cases of someone getting food poisoning from sun tea, but I couldn't find any evidence that this happened recently. Really, I think this is just paranoia. If you're a restaurant, sure, hold the sun tea. But otherwise, if you put the tea in the fridge once it's brewed, I think you're in the clear.
On a related note, I once had a house-mate who was an environmental toxicologist. He spent all day feeding pollutants to populations of mice to figure out how much you need to kill half the mice. (The LD50, in jargon.) He had this bizzare habit of roasting a bunch of chicken in the oven, then after it had been cooked, putting it on top of the stove to cool, and leaving it overnight. Then eating it the next day! Upon seeing the shocked and astonished looks and my and the other housemate's faces, he stated that it's actually pretty safe. All of the bacteria that was in the raw chicken (which can be pretty nasty stuff) would have been killed by the baking. And there are, according to him, essentially no airborne bacteria that can actually grow on cooked chicken and cause illness. My only proof that this is so is that he's still alive. I can't say I'm willing to try it, despite my happiness to drink sun tea.
Oh, and in case you missed in the news a few years back, the Five Second Rule is partially valid. If you drop food on a dry floor for five seconds, even one that's been walked on by people, it's almost certainly fine. Dropping food on a dirty or wet floor is another story, though. This is research from the University of Illinois, the fine institution where I went to grad school...