I presume if I had an unattended roadside vegetable stand with a cash-box, that I'd be able to prosecute someone who took vegetables without paying, certainly i

I presume if I had an unattended roadside vegetable stand with a cash-box, that I'd be able to prosecute someone who took vegetables without paying, certainly if they also made off with the cash-box. Why is this different on the web? I think it's mostly based on society's expectations. It is generally understood that the merchandise at a roadside stand belongs to somebody and another person should not take possession of it, while it is generally understood that something posted online where everyone can see it was posted with the intent of letting everyone see it. Given that, it would make sense that posting something everyone can see implies a grant of permission for everyone to see it. And if a written prohibition has no legal standing, why do so many companies pay lawyers to write click-through "terms of service" agreements? IANAL, but I would expect the "click-through" part makes a difference. A visitor to the site may not see a simple written prohibition, whereas accepting the click-though agreement at least indicates acknowledgment that those rules are there (even if they turn out not to be enforceable).