Of all of the numbers that are part of your daily personal life, which are important enough to keep private? Your Social Security number? Definitely. Your date of birth? Maybe — depending on how cautious (and how old) you are. What about your cellphone number? Probably, even though registering on the do-not-call list is supposed to largely insulate you from unwanted phone calls from people you don’t know trying to sell you stuff. But what about your ZIP code? These days, with the proliferation of …