You know what? I'll never agree the "omg you must be 18 to look at boobs" stuff. Do I understand it? Absolutely, but I still don't agree with it. When I was like 14, my sole purpose in life was to masturbate as much as possible, to the sexiest women I could find. Hello, internet :P
Why make some poor kid who's beating off 10 times a day use a sears catologue turned to the women's bra section? I was 50x hornier and 50x happier to look at porn when I was between 13 and 16 than I am now. Like it or not, I bet the biggest consumer of free internet porn is boys between those ages
And since boys between those ages are pretty much 100% internet savvy now, I bet 95% of them are frequent visitors to the big tube sites. Which probably explains their terrible conversion ratios
All the old men (the ones we sell smut to) have never heard of a tube, and still frequent thehun and google images to get their rocks off.