Now, I'm no opponent of nudity, but sometimes a movie throws a nude scene at you for no apparent reason and leaves you thinking "What the hell was the point of that?" (Straight-to-video 80's B-movies not included)
Open Water - The inspiration for this topic. It's a movie about two people stuck in the ocean after a scuba diving expedition. In a hotel scene (before the trip) the female protagonist is seen reading in bed while naked. And, as she tells her husband (or boyfriend, I don't know if this was ever established), she is not in the mood on this particular night.
Titanic - One of the most popular movies in history, and yet difficult to recommend to the grandparents who would blush at Kate Winslet's sultry pose. Not a good date movie when your date is a Mormon (long story).
Swordfish - Halle Berry's first nude scene was gratuitous, but clearly not pointless, as it probably accounted for 45% of the total ticket sales for the film. And I have a feeling most of the people who paid eight bucks for 10 seconds of Halle Berry's Boobs left feeling pretty blue-balled.