Obviously I'm against premarital sex for both moral reasons and for practical reasons. There was a
study reported on CNN that indicated that
one in four teenage girls have an STD. That is the fruit of a depraved society that encourages "feel good" wanton amoral behavior. The fleeting pleasure you derive from that selfish act of gratifying the flesh just isn't worth it. Are you truly going to be satisfied? Will that lead to promiscuity? Abstinence requires discipline, but many things in life require discipline. I'd rather be a virgin and wait until marriage rather than screw some chick who I'm going to forget in a couple of years.
From our Torah (the ultimate guide for living):
"If any man take a wife, and go in unto her, and hate her, and lay wanton charges against her, and bring up an evil name upon her, and say: 'I took this woman, and when I came nigh to her, I found not in her the tokens of virginity'; then shall the father of the damsel, and her mother, take and bring forth the tokens of the damsel's virginity unto the elders of the city in the gate. And the damsel's father shall say unto the elders: 'I gave my daughter unto this man to wife, and he hateth her; and, lo, he hath laid wanton charges, saying: I found not in thy daughter the tokens of virginity; and yet these are the tokens of my daughter's virginity.' And they shall spread the garment before the elders of the city. And the elders of that city shall take the man and chastise him. And they shall fine him a hundred shekels of silver, and give them unto the father of the damsel, because he hath brought up an evil name upon a virgin of Israel; and she shall be his wife; he may not put her away all his days. But if this thing be true, that the tokens of virginity were not found in the damsel; then they shall bring out the damsel to the door of her father's house, and the men of her city shall stone her with stones that she die; because she hath wrought a wanton deed in Israel, to play the harlot in her father's house; so shalt thou put away the evil from the midst of thee" (Devarim/Deuteronomy 22:13-21).