It also seems to suggest a certain gullibility?

I’m not sure that it suggest anything besides the fact that many people buying these products on Amazon also happen to buy other “fringe” products, perhaps because of paranoid tendencies.

Until something like this becomes mainstream, buyers will probably fall into two categories:

1. These paranoid types who are willing to try things most people won’t look twice at

2. Nerd/bio hacker types who have some fascination/interest in the subject

I’d guess there is only overlap when products are actually grounded in some real science, e.g. the people buying stuff for paranoid fringe reasons are also buying far crazier stuff that the bio hacker would reject outright and for good reason.