I make an effort to put the seat down for purely asthetic reasons, but if I don't it's no biggie. My wife knows how to operate the toilet seat so she doesn't care, either.
In the past, I've come across women who insist that I put it down because they were tired of falling into the toilet. Well, I don't know about you, but if you're going to plop your bare ass down on something without looking first, well, that's your own damn fault.
BB.