Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh. {Genesis 2:24} God designed marriage. He meant it to be a covenant {leaving and cleaving} and consummation {one flesh} of a man and a woman. Period.
Mark Driscoll believes that in his lifetime, we will see polygamy becoming legalized. We will see a bi-sexual being able to marry a man and a woman. We will see a Supreme Court upholding these unions, but they are not God's unions.
God is the first one who spoke marriage into existence in Genesis. Moses repeated it and Jesus and Paul proclaimed it. There are no blurred lines for those who claim to call themselves Christians. Sex outside of a union between a man and his wife is wrong.
In the Old Testament, the penalty for adultery was death. In the New Testament, the penalty is divorce and in the final judgement, it is destruction. God holds marriage by His design in high esteem, so it is wise that we do also.
Mark Driscoll preached a great sermon on adultery. You can listen to it HERE. He is very bold in calling sin "sin." Sin is always destructive. It always leaves scars and it always hurts someone. The healthiest place for people to have sex is in marriage. The healthiest place for children to grow up in is a home with a mother and a father. These things will never change no matter what lies society tries and tells us.
We must not become lukewarm as times become more perilous. We must stand upon the Word of God. He will have the final say. No one else. Don't be swayed by those who want to tickle your ears and compromise Truth. Base all of your beliefs on the solid Word of God and live.