It's clear that digital technology and smartphone apps have enabled new ways for vendors and buyers to do end runs around traditional notions of what is commerce and what is informal barter. Many people argue that these innovations both expand personal liberties and allow for more efficient use of resources. If two consenting adults want to put an economic value on an empty car or a vacant room, isn't that a net gain to both? Isn't this precisely what free markets do -- and why should government get involved at all? There are two problems, say critics. First, the whole history of capitalism is one of balancing the entrepreneurial impulse against hazards to consumers. The fact that some consumers may be innocent of the hazards is not a good reason to pretend they are not there.