I brought this question up with my friend, who suggested that we call the birth control pill the Pill because it is the ultimate decider of life and death. We use capitals when referring to "God", supposedly because he is the ultimate, he is the giver and taker of life. Thus it follows that we should capitalize in reference to the birth control pill as well. Importantly, however, the Pill does not take life, it simply prevents ovulation. It is THE giver and preventer of life.
Still, if I am the guy who invented the Pill, I am thinking I missed an opportunity.