Re:Health departments, condiments and the sick and demented
It depends on who I'm with, and how each of us is paying. If I'm out with someone I trust, then I'm good with having the bill together, and we each figure out how much we owe for what we ordered, plus tip. Sometimes one of us doesn't have cash, so instead of making the server split it between cash and charge, whoever is paying with a card will cover the whole thing and pocket the cash.
People I don't trust, though, separate bills all the way. Less hassle, less arguing, less feeling obligated to cover for someone who doesn't get it.
As to the condiments, I've never really thought about it, but you're right. I'm always careful about the tops (I was one of those kids, too), but it never even crossed my mind that someone could easily put pretty much anything they wanted into them.