When the established industry starts suing you, you know that they're starting to become scared of your disruption.
I think a barrier between the passenger and the cabbie is generally good.
I think a meter system or a zone system that is externally verifiable is better than some dude's cell phone.
After you spend 40-60 hours in one week schlepping people in your un-designed hack, an understanding will form of why modern cabs have fairly universal accoutrements.
I was referring to the idea that the medallion in Boston is a safety feature rather than a monopoly piece.