"Skirting" was a poor choice of word on my part. I didn't mean to imply they were doing anything unethical or borderline.

I simply wanted to point out that regulating cab companies and selling expensive permits is a source of city revenue. If an innovative new business disrupts that revenue, it may quickly find itself the subject of new regulation.

Now, if their success is based on efficient routing algorithms and higher-class service, then they have nothing to worry about. If it's based on the fact that they don't have one of the cab companies' major expenses, then they're at significant risk of being regulated out of profitability.