[drewcrawford]

> I have not seen any evidence that someone giving you one dinner during a trip qualifies as pay in exchange for work

You are approaching this from entirely the wrong direction. Your statement is like saying "I have not seen any evidence that so-and-so is innocent of the crime".

It is the presumption in the United States that someone applying for a "non immigrant" (visitor) visa intends to illegally immigrate to the United States. And so it is the burden of the visa applicant to prove otherwise.

There does not need to be any evidence that one dinner during a trip qualifies as pay for his entry in the United States to be lawfully denied.