(Updated 6:00pm with 3Taps response) Craigslist has followed up on earlier threats and filed a lawsuit against popular apartment listing site PadMapper. The case raises questions over whether Craigslist is stifling innovation or simply protecting its data. In a complaint filed in San Francisco, Craigslist is accusing PadMapper and “one stop data shop” 3taps of a slew of infractions, including copy