Personally I think that "study" is BS. It's akin to the ones that say that eating peanut butter causes cancer.
Microchips are basically inert materials, since it's contained fully within the outer casing. It's like a teeny bit of glass embedded. The worst it should cause is minor irratation, or possibly scar tissue.
I've worked around animals and vets for many years, and I have never yet seen or heard of any pet having a tumor due to a microchip. A phone call to the local vet university resulted in laughter at the idea, and a bit of advice to "not believe the supermarket tabloids". I'd guess that means they don't believe it's a concern.
As far as whether or not any particular person wants information embedded in their pet, child, self, or car, I'd say it was a personal decision.
My pets are microchipped, and I will continue getting them microchipped. I think if there were a system in place for microshipping children, and I had children, I'd have my kid microchipped too.
Most chips only are the equivalant of "bar codes". They don't really 'transmit' and you can't track them via satilites and such. I've been told fantastic stories by clients about them, you wouldn't believe. Some of them still believe that a microchip can train the dog.. no.. seriously.
All in all, it's a high-tech I.D. tag that can't easily be discarded. I'd love to see more snakes embedded. You certainly could I.D. a particular individual snake easier than comparing photos to markings.
Cheers!
Theresa