That is an interesting question. I believe that if you'd do something like that, it would mean that you were looking for reasons to have a problem with your significant other. To have an excuse to separate or creat discordia between you two.
Now I have to admit that I did have a similar situation, however it was not me who set up a "trap" for the person I was seeing. At the time I did not know, but a possible BF was approached by a girl over the Internet (hi5, msn). When things got really hot and future between my possible BF and that girl was discussed, I was let in on it. I didn't put a halt to it. I wanted to see how far he would go chatting on the Internet with a girl he had never met in person. To make a long story short, he went far enough for me to get out of that relationship. I was so disappointed in him. He tried to make excuses for it, I did not react, I totally blocked his presence out of my life. I spoke to him again 6 months later after I received an unexpected call from him. He deeply apologized. May-be I'll forgive that mistake one day.