I suggest that a lot of your concerns could be put to rest by allowing people to have multiple identity cards/chips. Just like we can have multiple PGP keys now, multiple IDs would allow people to participate in diverse activities and make it hard for a malicious government/whatever to correlate their activities.

This is not to say that we should all have multiple identities, just multiple identifiers. Sort of like having three licenses with the same photo and description, but different numbers. This should make it much harder to track people through all their day-to-day activities. Of course the tax office would have to have the details of who owned what identifier-number, but there would be no reason for anyone else to. This would stop say your employer from finding out where you went partying last night, but federal agents could still flag certain IDs.

Of course no one in their right mind would implement this system because the whole idea of a ID card/chip is to intrude into peoples privacy, not protect it. I suggest this is why anonymous digital money will never take off either.

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Jeremy
I didn't believe in evil until I dated it.