[Martín Zalacaín]

It is harmful for society, imo. Sex before marriage raises the odds of single mothers, which is dangerous for society if it becomes a major trend. Furthermore, premarital sex is usually a means to obtain pleasure, with no desire to procreate. This can result in an impact on demographic figures, as can be seen in european countries today (I'm not implying that this is the only cause behind our disastrous birthrates).

I think of morality not as eternal values, but as a set of shared rules of conduct that help society to function better. Following this definition (that I just made up, don't take it too seriously), it would be immoral.