As a well-endowed female, I've had my share of men talk to my cleavage rather than my face, and only once have I had the nerve to say, "If you want to know what my bra size is, why don't you look me in the eye and ask me?"
Let me be clear from the start: sexual harrassment and objectification of *either* gender is NOT acceptable. Within that framework, though, I have to admit - and I'll probably get flamed by the sisterhood for this - that I love my cleavage, and a man talking to it merely amuses me. I'm a gleeful exponent of the 'four millisecond' rule: every male, straight or gay, looks at a woman's cleavage for 4 milliseconds before looking up. If a guy breaks the four millisecond rule (i.e., looks for longer), I tend to assume he's straight. Having serious cleavage is great gaydar confirmation.
I suspect I'm not bothered because I'm not a beautiful woman (the only way I'll stop traffic is by using the crosswalk light at pedestrian crossings), so I don't get stared at and treated as an object/commodity. I'm pretty enough for all normal purposes, to quote "Our Town", and that's good enough for me. The guys staring at my chest whilst talking to me already know me and are interested in what I'm *saying* whilst admiring my assets, which is a different kettle of fish from the leering stranger with a drink in hand.
For the latter type, chaperone cat with sharp claws would be extremely useful:

I love the wee added comment on icanhascheezburger:
but her eyez r sew purtee.
So, guys, don't forget to look up - you may even find out more than just her bra size.