We do not have a say on anything a caster other than us does. If he/she chooses to do a spell to break up a couple then so be it. That is them and not you and I do not know why any of you are calling this person evil. Yes, I am against doing spells like that but I would not think any less of others who do those spells .
As TheColiation said, maybe we all should think about the reason for the spell being cast. Was it an abusive relationship? Etc.
However, going back to the original poster, it seems that my above comment doesn't apply to this situation. Do you have a reason for asking this? Did you cast the spell for a logical reason or just to mess up a pair of lover's day?
To Urlic, Karma does not apply in this life, it applies in a person's next life. Karma would have no effect on the person in this life, only in their next life, and that all depends if the person believes in the Hindu concept of reincarnation. Society today has the wrong conception of Karma.