Privacy is what allows us to eat pints of Ben & Jerry's ice cream in a single sitting, to cheat on our spouses, to pick our noses, to watch porn, to abuse our children. Privacy facilitates all sorts of unsavory, unethical, and even illegal conduct.
His main goal is to bring his weight back down to his "fighting form," which strikes me as very Bridget Jones. But he does have other worthy goals as well, and exposing his progress to the world probably will help him accomplish them. Good luck, David.
My bad habits: junk food (especially fruit snacks) and general procrastination. I'd get a lot more reading and writing done if I had to post my progress online every day. What bad habits would a lack of privacy help you break?