everyone is poly
This is an interesting thread.
In my opinion, infidelity is not what brought us to being poly. It's what forced us to get comfortable communicating openly and without fear of loss. That transformation has opened up our lives to endless possibilities, polyamory being the most intimate and difficult to summit without that level of clarity.
Rarechild and I have fallen in love all over again, not because we have decided to open our hearts to others, but because we have, for the first time, opened our hearts fully to each other. And damn, that feels good.
I believe that everyone is poly, but most never get to be open about it (with themselves or their SO) because of the preconceptions we're taught as children. We all fall in love with different aspects of others all the time. It comes in the form of admiration, respect, lust, trust... (insert attractive attribute here). People who declare themselves poly have simply decided to live that love openly and allow it to develop as fully as possible.
Just my $.02