@neil You raise an interesting question.
I have been interviewing people on camera for our History of the Internet project.
We have them sign release forms.
But there is also the recording of public statements - for which one usually does not need a release form (but it is often polite to get one.)
The question I have is what is the boundary, with regard to use of the recording, between recording a person's image/voice via Meta style glasses and a recording of someone giving a public statement?
Is the boundary related to a kind of implied consent by one making a public talk?
I know that this is going to vary, a lot, between countries and even between divisions within countries. (E.g. California has a law about people controlling use of their personas, images, and such - https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CIV§ionNum=3344. )