I doubt the chip can ever be made mandatory here in the U.S.A., but with the recent PATRIOT ACT zest to intrude on civil liberties and privacy I dunno, makes for some scary thoughts. I can only imagine millions of people taking to the streets in protest of being mandatorily marked this way.
A smart I.D. card is capable of digitally carrying health and other personal information. No need for intrusive surgery this way and it can still be effective even as a voluntary device.
As for the mark of the beast, well I would have to first off believe in the beast in order to beleive that the chip is the mark. Since I dont it is a mute point.