The reason so much disruption comes from "barely skirting the law" is because government sets up the law/regulation to entrench these old business models. So much of what the US government does today is in service of big business, not necessarily adhering to whatever moral standard you have in mind for the rule of law.

Uber has to use the gray areas precisely because regulation was set up to prevent disruption of the cab industry. This regulation inhibits growth and promotes stagnation, evidenced by the fact that NYC cabs did not accept credit cards until 2007 and by how obviously under-served the SF cab market was.

Uber, by skirting the laws that were not serving the consumer but rather entrenching an industry has been able to do more in five years than the entire taxi industry has in 50.