My opinion
I used to think the mark of the beast would be a chip or something, but now I believe it is more symbolic. A chip would be in my hand or in my head, but not on them and the Bible says it will be a mark ON the hand or head. If it were a literal mark, I could easily slice it off my flesh with a knife if there were no alternative way to getting it off. If I had the mark removed by surgery or slicing it off, it wouldn't be permament. I also don't think God is going to literally put a mark on his followers like it says in Revelation. By that I mean, I don't assume he'll put the word "My servant" on our foreheads. I don't think the mark is the main focus of what's going on, but who our allegiance is to. It is either to God or to satan.
I'd like to hear more thoughts because I don't really have a conclusion :-\