OK. I've seen a lot of funny answers here so I'm going to give an honest opinion.
If you see it on the street in most neighborhoods or see it in a public forum, it should be allowed. If the only place you can see it is in a "Gentleman's club", maybe it shouldn't be on a forum for the general public (mainly so some censor doesn't get the mods and site in trouble). Looking at South Beach, I'd say that doesn't leave much you should limit. Then again there is always New Orleans and a lot of biker parties that don't leave much to the imagination in public forums (or should that be pubic forums?).
Now that being said, I do have a picture of a very pretty model sitting on a car in a public car show for new car models. I guess she didn't want panty lines on the form fitting dress but forgot she had on a short dress when she sat down. Made for a very nice public photo.