Do you believe in monogamy?
In this day and age we see more and more people having affairs. From those with disastrous political repercussions to those that never see the light of day, although sometimes it can be symptomatic of a relationship that just isn't working. I have always thought that humans by nature are not monogamous, it is cultural and societal constraints that have made monogamy the normal and accepted standard, for the most part, in formalized legal romantic/arranged marriages.
I am not necessarily saying that one is better or more 'right' than the other only that generally, as a species of the homo genus, we are not naturally monogamous. A rather biological view yes but that's just my humble opinion.