I don't think there is anything "morally wrong" about sex before marriage.
However, I'm not a sexually "free" person. I've only ever had sex with one person, ever, and she is the person that I'm marrying as soon as gay marriage is legalised in New York, where we live and want to get married.
People can choose whatever they like; it doesn't change my opinion of somebody if they have sex before marriage or not. However, for me, I have huge trust issues and I find it impossible to separate love from sex, and have never wanted to have sex with anybody outside of my fiancée. So, for me, I'm more of a "I won't have sex unless I am PLANNING on marrying" you type of person, but I don't look down on anybody who doesn't practise the same thing I do.