First of all, what is the mark? There appears to be much confusion and fear, based on ignorance of what the Bible teaches on this subject. I have heard and read stories of people who refuse to have anything to do with the number 666. The number by itself is nothing to be afraid of; it comes after 665 and before 667. There are also people on the internet who are associating it with microchip implantation. My response to that is that it could be, but it is too soon to tell.
There are conditions for truly having the mark, as set forth in Revelation 13:16-17. Whatever the "mark" is, it must be in a person's right hand or forehead, in one of two ways: the name of the beast or the number 666. Anything that does not meet these conditions is NOT the mark and is nothing of which to be afraid. It will be some kind of mark on the skin. Would a microchip implant leave a mark?
Now to the question at hand. What will happen to people who decide to take the mark? Let me say, first of all, that there will be much motivation to do so because without it one will not be able to buy or sell. Revelation 13:15 warns that people who do not worship the image of the beast will be killed. However, anyone who does decide to take the mark is deciding against Jesus, and for Satan, for all eternity. There will be no turning back. It will be a done deal.
People who take the mark will experience the full wrath of God as well as eternal torment. This is taught in Revelation 14:9-11. "And another angel, a third one, followed them, saying with a loud voice, 'If anyone worships the beast and his image, and receives a mark on his forehead or upon his hand, he also will drink of the wine of the wrath of God, which is mixed in full strength in the cup of His anger; and he will be tormented with fire and brimstone in the presence of the holy angels and in the presence of the Lamb. And the smoke of their torment goes up forever and ever, and they have no rest day and night, those who worship the beast and his image, and whoever receives the mark of his name.'"
In addition, Revelation 16:2 says that during the Tribulation Period, those who have the mark will experience loathsome and malignant sores. They will also experience the rest of the plagues mentioned in this same chapter, depending to what degree they survive.
The day is getting closer when the mark of the beast will be implemented. IF, and I say IF, microchip implantation is the mark, one source on the internet says it will be completed by the end of 2017.
There is great reward, however, for those who will refuse to take the mark. Revelation 20:4 summarizes it this way, in the vision that God gave to John, the author of this book. "And I saw thrones, and they sat upon them, and judgment was given to them. And I saw the souls of those who had been beheaded because of the testimony of Jesus and because of the word of God, and those who had not worshipped the beast or his image, and had not received the mark upon their forehead and upon their hand; and THEY CAME TO LIFE AND REIGNED WITH CHRIST FOR A THOUSAND YEARS." (emphasis mine)