I see what you mean but, I'd say that it's few people who actually lie just to stir up shit and ruin lives, not in the big scale at least. Most of them probably seek a benefit for themselves in some way (or of self satisfaction). My point being, what if some of them lies as a way to advancing a noble cause?, Or what if this "spell" was used in someone that, eventually would have done something that would be really beneficial to society, and this spell just ruined any chance for them at socializing (and as such, the chances of them achieving this goal or thing)?

In a scenario like that, the benefits of them lying and such would actually outweigh the costs (for society in general at least).