I think that given the right situation or the right amount of temptation anyone will cheat. Most conditions being a mutual understanding with another person, a lack of something that can be fullfilled elsewhere, or quite possibly the over-SEXed factor. The over-SEXed factor being a person finding themselves in a situation where you literally smell sex. Let's say for instance a room full of naked horny cheerleaders or for some a room full of naked and horny Vin Diesel knockoffs.

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Deep into that darkness peering,
long I stood there, wondering, fearing,
Doubting, dreaming dreams
no mortal ever dreamed before.