hubpages suggests:
"It's a fact that most of the men idolize big breasts. Every year women spend millions on breast implants and other cosmetic procedures to improve their breasts including enlargement pills, pumps and creams.

Considering the role that big breasts play in our culture and society, the amount of time, energy, money and emotion that goes into breast enlargement seems justified.

But why do men like big breasts?

Evolutionary biologists have discovered that a lot of the physical traits we consider attractive have a sound basis in genetics. How does this explain the male fascination with big breasts?

According to evolutionary biologists humans are the only primates that have sex face-to-face. All other primates choose the front-to-back position. Human females are along among the primates in having large breasts even when not nursing. Evolutionary biologists theorize that large breasts look like a butt! Crazy as it sounds, all the evidence fits: all primates are turned on by butts - except people. Only humans have large breasts and mate face-to-face. Therefore, maybe big breasts evolved in imitation of buttocks.

Or is it all just marketing? Some sociologists scoff at the evolutionary explanations offered above. They theorize that the male fascination with big breasts is driven by the advertising and media machine.

Their explanation goes like this: children are exposed to seductive, sensual sexy advertising featuring busty female models. Children are taught to associate these images with arousal."