That makes sense but I don't know if you can really draw a parallel between email and these devices: (1) Sending email is nearly free, creating devices is not.

That makes sense but I don't know if you can really draw a parallel between email and these devices: (1) Sending email is nearly free, creating devices is not. Not sure if the economics match. (2) False positive filtering matter because spammer need to manually reply to emails, creating more work. But with these devices this is not the case, it's all automated. There is no need to filter out smart people.