My point isn't that stupid ideas don't exist, but that the great ones seem stupid. Dropbox was criticised on here; many thought AirBnb stupid.
The fact that we do not hear about even more horrible incidents regarding this service is for the most part due to society being overwhelmingly composed of more or less moral individuals (with an active remediation and PR campaign from the incumbents as a distant second reason). But I find hard to believe that anyone who can do any half decent risk assessment would sign in for that kind of liability.