Ok, morals, rights, laws.....all good points. He wanted candid shots....this has become difficult as people have shown.
If you ask me....the best Idea I saw was the person mentioning to take pictures of many things openly...and ignore those of "posed" individuals. Maybe even take their picture, but don't use it.. spend some time there taking pictures of the product, the store front, the tables, the chairs. Obviously the owner will then be unhappy if you have not notified and asked permission.
The point is, you CAN take pictures candidly without looking like you are a Privat Investigator. If I walk into a shop and see a person taking pictures of everything, I wouldn't think tiwce i I happened to be in a shot or too. I would move on with my day. If busy body becky decides to demand yout o stop let her know that you are using it as a hobby and are just trying to improve your skill, then let her know you have the owners permission and that you will not take any more pictures of her if she does not wish.
It's kind of the whole "deer blind" strategy. you place the feeder there....let it sit a few months....let them get used to seeing it and feeding from ti...then you place your blind out there, let them get used to that. maybe before the season starts you visit the blinda few times and spend some time in it. things become a routing for them and before you know it....WHAM they didn't have their guard up and you got your shot
(side note I do not hunt, and have never shot a dear myself, my uncles and co-workers are CONSTANTLY ranting about this, but I just don't have the money or desire for the hobby)
that's my 2 cents