It depends on if I'm interested.  But every woman on the planet has a cleavage, and if I spend all day looking at one, I'll miss all the others.

My message to women is this: If you don't want people to look, don't show it.  If you do show it and someone looks but you don't like it, on what basis could you complain?  That you're a hypocrite?  Sure, someone may be a jerk about it and stare, but that just means there are two jerks in the room.  This argument is ridiculous.