So here’s my take: Cab fares are in the cross-hairs today but that’s just the beginning. Starting with Millennials, car-service apps can jumpstart carpooling, redefine ride-sharing and undercut the logic of single-occupancy driving. Here’s hoping Uber’s Bad Boys don’t turn people off, because Massachusetts needs to encourage these new services — while stoking competition among them and setting minimum safeguards for customers and drivers. The prize is lowering the CO2 costs of passenger trips, a big win in the fight against climate change. Thoughts?