I have always wholeheartedly agreed with the SDA/sabbatarian position that the Mark is sin, not literal chip (though I disagree that the Sabbath/Sunday will be the issue), and I used to argue that there would therefore be no problem with taking the smart card (that was when that was the main candidate for the mark, and before they started really talking about chips). But now, having matured some from my early days, I still believe that the mark is sin, but still would not trust any chip. Not only do I not like the idea of some foreign object like that in the flesh (which might be uncomfortable, or if placed in wrong, even cause infection, etc), but if the system has gone evil, and is enforcing a "spiritual" "mark", this chip would still be used by them to control you, and force you to do what they want, even if you are in hiding and forgoing buying and selling! Plus, it would still be a sign of alliance with the evil powers, whether or not you are committing whatever sin/renunciation of Christ they are trying to enforce.
In fact, I believe the "scorpion stings" of Rev.9 (It can be clearly shown that the scorpions out of the Bottompless pit represent the Beast power) could actually be such an implant. Notice the stinging is only done to the ungodly. This may not be the actual "mark" of sin, but it could be an implant or something that will be ultimately used by the Beast.