Right now, mammograms are targeted only for the over 40 population. For women under 40, feeling your boobies is one of the primary ways to ensure early detection. Somehow telling young women the importance of "self-breast exams" doesn't quite have the same punch as saying "feel your boobies." So you might laugh at the slogan, but hopefully you'll take it seriously and do it... and so will those who see your t-shirt.
Also, the site is built with Homestead, a product I helped build back in the early days of the Internet boom! Anyway, I'm not asking for sponsorship for the walk because there's really not much time until the race (though tax-deductible donations can be made at the SFKomen web site linked above). You can also buy awareness-raising shirts directly from the Feel Your Boobies store.