It's a little more complicated than that. The regulations surrounding 18USC2257, which covers the filming of sexually explicit material (and disclaimer, I am not a lawyer nor do I play one on TV), is pretty clear in the fact that anyone who appears on camera must be included in the records filed by the production house for said video, which includes verification of being over the age of 18, having a valid government ID, and a few other bits of information. Obviously, random passersby have not provided this data and not having it on file is a felony.
The question then becomes, are foot/tickle fetish videos actually under the jurisdiction of 2257 laws? I don't know, and arguments could be made in both directions. The fact that these videos are being sold on Clips4Sale and posted to PornHub - which does require 2257 compliance - makes for a pretty good argument that they do. All I know is, I don't want to have to be the guy who has to defend it in court.