> Suppose a Wall Street Journal reporter were also dining at the restaurant, saw the conversation going on, and then published a story about it.
This is explicitly considered by the SEC. Indeed, from their guidance on the matter-- read the last clause ;)
Of course, note this states "include" for recognized channels of distribution; there are other means by which information can become public. But "can be found out by the public" and "are broadly disseminated to the securities marketplace" are different standards.
> All information about the Company is considered nonpublic information until it is disseminated in a manner calculated to reach the securities marketplace through recognized channels of distribution and public investors have had a reasonable period of time to react to the information. Generally, information which has not been available to the investing public for at least two (2) full business days is considered to be nonpublic. Recognized channels of distribution include annual reports, prospectuses, press releases, marketing materials, and publication of information in prominent financial publications, such as The Wall Street Journal.
Also note-- e.g. your buddy Tom who has signed a nondisclosure agreement tells you that they loaded 50 trucks full of product today-- if you trade upon this you are probably committing insider trading because the information was misappropriated.
But your friend Bill who was sitting outside the factory on public land watching the loading can trade upon it freely.
You can't trade upon it until Bill's news story has been out for 2 full business days, because you already know the material nonpublic information by virtue of it having been misappropriated.