Voyeurism is the practice of observing someone else nude or engaging in intimate behaviors without that person's awareness of what is going on. The common stereotype is that of the Peeping Tom, for better or worse.
Exhibitionism is the intentional public display of body parts that are normally concealed.
Both of these are officially categorized as paraphilias by the American Psychiatric Association when there is sexual intent involved.
Lately, the media has become increasingly an enabler of these sorts of practices, whether the person being viewed is complicit in the process or not. (Does anyone believe that many or most of those "wardrobe malfunctions" were purely accidental?) As a matter of fact, there's a purely instrumental reason why there's been a proliferation of these types of literal exposés: they're translated into increased magazine sales and increased publicity for the person in question. For example, there's been a recent proliferation of personalities who have won clothing that makes it evident that they went commando, yet managed to expose very little. There's a mindset in Hollywood that perceives that there is no such thing as bad publicity.
However, there are some occasions when a person does have a legitimate malfunction. When that occurs, the polite thing to do is to pretend nothing happened, nothing was seen! Common decency and good manners should call for that.
There's a semantic issue involved. The routine media coverage of these showings indicates strongly that the social climate towards these activities has shifted, making certain of these more normative. And, should not there be a redefinition of the psychiatric term as it is ordinarily used? Or maybe there should be some kind of additional qualifications as to when these terms should be used?
How about attention whore syndrome as a diagnostic category? Well, the present-day histrionic personality disorder could effectively cover it. But the deliberate publicity-seekers might warrant such a distinction!
To use a concrete example: If someone were cheekily to appear in public at South Beach while wearing a thong, should that be considered exhibitionism? Would the beach visitors who visit that shore to enjoy the local fauna be regarded as voyeurs? This is a long way from Daumier's keyhole peeker above. The thong-wearer presumably intends this sort of exposure, and the local custom permits this kind of display and its viewing.
And, in the case of Mardi Gras in the French Quarter, temporal criteria possibly.
nd time plays a part, too.