Isn't fooling someone, in fact fooling yourself? Why would anyone feel the need of fooling someone? There are or can be a lot more questions around this subject, but one thing can be said before further discussion: Most of the time, or let's exaggerate, at any given time, fooling someone would be originating from only one point, namely, personal interest, benefit, and other synonyms of these. As far as I'm concerned, this statement is the furthest man would get. One does not simply discuss the morality or utility of it on any level of conscience.
Speaking personally (or writing, technically), I don't like fooling anyone. Yes, I do it sometimes, indeed. But the fact that it makes me feel guilty or upset remains the same regardless of whether or not I give a damn about who I believe to have fooled. One would be expected to feel bad in case it is somehow revealed that he/she has tried (yet failed) to fool someone else, they will be shunned, lose credibility and trust. However, if it is not discovered and he/she, so to speak, got away with it, then only he/she knows the truth, what actually happened - thank you Captain Obvious. Very little things may be forgotten or forgiven; no one would care. Nevertheless, what one has done, is still a burden, heavy or not. And one would be fooling no one but him-/herself by ignoring this fact, believing that it is nothing.