Semi-formally (and game-theoretic understandings should generate this independently) your best course of action is to defect only where pr(found out) * disutility of being found out < gain of defecting - gain of cooperating.
Yes, but only if you're selfish. If you're an idealist, then "your best course of action" might be to play by the rules even when P(caught)U(caught) << U(D) - U(C).
Note that this issue is harder than it looks to define away -- if you define utility in terms of some ideology (international socialism) or species (humanity) so as to include your preference for playing by the rules, then we can still worry about cases where people of good faith but different ideologies (Spanish Civil War) or species (Three Worlds Collide) are trying to work together. In those cases, your urge to play by your own flavor of altruistic rules is in conflict with tropes like honesty, honor, and symmetry.
Institutions like markets can accomplish a whole hell of a lot with people who always cheat around the edges, but there are a few, erm, edge cases where it's really handy to have a couple of reliably honest people around. Somebody has to watch the watchers, and it probably doesn't hurt if they truly believe that God is watching them.
Even theistic people unconsciously perform this operation - witness the cases of evangelists thinking they can hide it.
I suspect that fundamentalists who take vacations with rent boys just have bad character; there are plenty of religious people with bad character. My claim isn't that religion does make you a better person; my claim is that religion opens doors to self-improvement techniques that make you a better person. Any given theist still has to invest hundreds of hours in learning and applying the techniques in order to see any benefits. Most of 21st century organized religion is very bad at screening out religious leaders who don't learn or don't apply the techniques.
I've long entertained a dubious regard for the practice of lying to children about the existence of Santa Claus. Parents might claim that it serves to make children's lives more magical and exciting, but as a general rule, children are adequately equipped to create fantasies of their own without their parents' intervention. The two reasons I suspect rest at the bottom line are adherence to tradition, and finding it cute to see one's children believing ridiculous things.
Personally, I considered this to be a rather indecent way to treat one's own children, and have sometimes wondered whether a large proportion of conspiracy theorists owe their origins to the realization that practically all the adults in the country really are conspiring to deceive children for no tangible benefit. However, since I began frequenting this site, I've been exposed to the alternate viewpoint that this realization may be good for developing rationalists, because it provides children with the experience of discovering that they hold beliefs which are wrong and absurd, and that they must reject them.
So, how did the Santa deception affect you personally? How do you think your life might have been different without it? If your parents didn't do it to you, what are your impressions on the experience of not being lied to when most other children are?
Also, I promise to upvote anyone who links to an easy to register for community of conspiracy theorists where they would not be averse to being asked the same question.