From my observation, I always hear people getting food poison from already cooked foods. Their claim was always that the meat was under cooked. I don't have any scientific evidence, just my experience to base off of. I strongly believe why people get "food poison" from cooked food is really because the fat went rancid. whether its the cooking oil being recycled,thawing & refreezing unused meats or poor handling.
My step-sister and her friend's brother both got sick from a chicken burger that was cooked (and not undercooked). It's the only time I've heard of someone getting salmonella, personally.
A while ago, my college was having issue with people feeling ill. It turns out that the cooks weren't doing their job at handling meat properly. They'd store already cooked meat with uncooked. A lot of the time, my hamburgers weren't cooked through. I had gotten sick, lightly, as a I tend to have a very good immune system, quite a few times from it. (Although I also get sick from the quality as well, another issue they were having. They tried to fix it--provide more healthy food, but now its under the pretense of healthy, but still extremely processed and now quite bland. I don't generally eat at the dining hall, prefer the commons area, where there's a food court, because the quality tends to be marginally better.)
I should check to see if my college's sushi is always cooked. They have tuna and some other raw fish sushi once in a while. I should probably check the smell as well. When I studied sushi a little (as a small hobby), I read that if a fish smells fishy, it has started to rot. Sashimi should not smell fishy. When I've had it, it's usually not.
This is something I've also wondered a little about--how to deal with parasites or illness. I'm frankly not too worried about salmonella. I have great luck with bacteria and viruses, as a rule. (When a lot of my friend and boyfriend got H1N1, I didn't. Subsequently, my bf got 3 colds and 2 flus, one being H1N1, over this past year, none of them he passed on to me.)
Also, what about E. coli?