I think the fear has an underlaying motive. I think it goes deeper. Lies told to hide mistakes are from fear of the consequences of those mistakes. To face those consequences would make the person unhappy. Lies told to hide emotional betrayals are from fear of hurting another, and that other perhaps hurting you. To get hurt makes one unhappy. Lies told to boast or boost one's self are from low self-image, and a fear of how others may perceive you. Having others not respect you can make you unhappy if you fall into the false perception of perceiving yourself through the eyes of others. Lies told to acheive gain are based on greed, which is based on a survival instinct -- the "I need it all -- just in case" type of thinking. It's tough to be happy if you are dying from want. There are other types of lies, and reasons for them, but like you have posited, they are based upon a fear -- and that fear, ultimately, is based on the fear of losing some sense of happiness (or at least contentment). Ultimately, then, the lies based on fear are told because, I guess, in some way the person thinks that if folks beleive it, it will make the liar happy -- by avoiding a consequence, boosting their ego, or assuring their survival.