Obviously this is just a discussion and nobody will ever know the answer, but what % of people do you think cheat on their partners?
Before my ex cheated, I would have bet my life on him not 'being the type' I would have sworn that he would never do that to me etc. etc. over the years nothing fails to surprise me any more and I am much more open minded that it happens A LOT.
I would guess at 90% of men and probably about 70% of women. I am basing this on knowledge of people that I know.
This is one of the reasons that I probably wouldnt enter into a serious relationship again, unless I wasnt expecting it to be exclusive...