I was riding home on Main street between MIT and Central, and there was a cab parked in the bike lane, despite there being tons of open parking spots. I growled under my breath, checked for traffic and rode around him. But three or four cars past that was a police car, parked in a normal spot while the officer checked something on his computer. I rode by, then stopped and circled back. I knocked on his window and said "Can I ask you a favor?" "I can ask that cab to move out of the bike lane, but I bet he'll pay a lot more attention if YOU do it." The silver haired, crinkly blue eyed officer smiled and said, Sure, I'll do it.
I wasn't sure if he meant right then, or whenever he finished what he was doing, and I didn't want to sit there impatiently, so I thanked him, told him "that would make my day" and started to turn around to ride off. Immediately he got out of his car and whistled to get the cabbie's attention, walking towards him.
I didn't stick around, but when I looked back, the cab had pulled into a parking spot to wait.
Win! Thanks to Cambridge's finest, who I have nothing but good experiences with.