Promiscuity is often denounced.  I don't see it that way.  It may be (actually it certainly is) a waste of time and a manifestation of insecurity (a need for constant reaffirmation that one is desirable) or maybe some other similar psychology, but it in itself is not evil or a sin or even bad karma.  If it is done with the main objective being to give one's partner pleasure, then it is actually good karma.

Where it gets ugly is when it involves infidelity (one is married or engaged and one has promised fidelity), since then it becomes lying and creates the likelihood of hurting someone.  Of course it also becomes ugly when precautions against disease spread and conception are not followed carefully.

The modern college student (especially young man) in the big cities of Vietnam finds himself in a sort of candy shop, and often prudence goes out the window (I never heard of a prudent college student anyway).  Men are safer with multiple partners, but women can produce a danger to themselves since some men are violently jealous after even one tryst.  This is grossly unfair, I know.