An implanted chip... like anything else, I expect a whole cartload of unexpected consequences. Tamperproof? Nothing is "tamperproof." No doubt people will be able to disable the thing easily (if nothing else, with a sharp razor and tweezers). Fruad should be easy to implement, at least at first, until scanning devices get more complex. Any health risks having a foreign object under the skin for a long time? A transmitter the size of grain of rice isn't much - a 100 billion of those rice grains wandering around the environment, though, could be an interesting waste product concern. Not to mention what happens during a blackout. Or walking by a large magnet.
My opinions don't even fall on the tagging (for now).
My concerns are in the links at post 1.
Funding for these projects are being made possible through grants from the NGOs.
The CFRs have clauses of default for these grants giving ownership to the Grantors. Terms of sale, use and transfer are controlled by the grantors.
The Grantors are the NGOs, IOW, the UN.
The NGOs created partnerships with our government entities to collect the data and filter the monies.
Are we still the USA? Or are we now a part of the UN?
And the health risk questions you ask can be read from here:
http://www.nationalpropertyowners.org/nais.html