"Trust, Charney argued, isn't a black-or-white thing." Wrong - it is binary - but does depend on the impact of what is being trusted and to whom.
"It may be perfectly OK to trust an unknown street vendor with a credit number" - Well, you're a damned fool if you do without taking some scaled precautions. You may find you're liable under your CC terms and conditions.
"that caps fraud losses at $50". Who's loss? It may be the max the card holder might directly lose but the credit card company may not be able to recover the money you lost it. Indeed, the credit card insurer may have to raise premiums and, thus, either way I get to pay increased charges.
"Turning over a bank-account number to the same salesman might be altogether different." Well slap me down with a fish - I didn't think about that.....!
Seriously though, as other posters have noted, this isn't about protecting the"average Joe" punter its about protecting the corporate entities and making the cost of entry so high that only the most persistent, expert, or largest can rip you off.
It is a tool, not a Silver bullet. In time it will be circumvented and is just another step in the arms race.
MS are selling but in doing so are changing the pitch & stadium so that the rules have to change. They can do so because they are, in effect, the only game in town. You may not like it, you may strongly object, you may do all sorts of things but you are unlikely to be able to change things.
Security is mainly a personal thing. Look after yourself, press your Government and politicians to look after your interests but DO NOT expect commercial enterprises to be altruistic or you will be unsurprisingly disappointed......