Picture this. You’re sitting in an airport terminal. Your flight is delayed because the pilot’s astrological sign doesn’t align with the baggage handler’s, and you just want to check your email or read the news on your iPad. You open your Wi-Fi settings and see an oasis: “FreeAirportWiFi.” You click it, feeling like you’ve won the digital lottery. But connecting to free public Wi-Fi is essentially the digital equivalent of shouting your social security number…