The way I look at it (so to speak) is,
If you intentionally draw attention to something, you automatically waive any rights you may have had not to garner that attention.
The fact of the matter is, a well-presented cleaveage is eye-catching. That's not to say we're all pervs, it's akin to someone driving past in a bright red Ferarri or something. If you don't want attention, you can still drive a nice car (to continue the analogy) without having to put 'look at me!' neon lights all over it.
If a young lady has an attractive figure and wants to put it on show, she really can't then complain if she gets admiring glances. If she's doing it to be 'comfortable' then she can still wear flattering clothing that doesn't advertise quite as obviously. I'm not suggesting that everyone who doesn't want to be leared at should wear a burka, more that there's subtle and blatent ways of wearing, say, a low-cut top.
All that said, sticking your nose between them and going "flubbaflubbaflubba" is probably to be considered bad form. Certainly on your first haircut anyway.