Does that include smartphones and collateral (incidental) subjects? I had run in to this a few times. When doing street photography. (using a DSLR) . With the invention of the smart phone and so many folks taking pictures with their family and friends out in public, some questions arise.
Is there someone in the background who is still in focus? Since the are recognizable , did you get their permission before you put that photo on Facebook , Instagram, etc? Or did you take the time to crop or blur them out?
You say accidental, I say maybe they were the intended subject and you just used your friends to cover aiming the phone in their direction.
Hard to hide intent with a 200mm lenses, but very easy with a smart phone or tablet.
I used to have a negative with regards to camera on smartphones, but not anymore. The constant use in public has really muddied the waters with regards to expectation of privacy in a public place.
I am working on an exhibit now, and I will definitely being using releases from the subjects portrayed, but only for those used . Any that never make it off of my studio walls do not require a release, although 5 dollars toward a hot meal is always appreciated.