1. The most interesting information for me was, that the well-known facts about liars are wrong.
2. In my opinion, people tend to lie about doing / not doing something (like in the example with gorillas or children) so they do not get into trouble. Or for example, when it comes to hiding some facts - good ones, like birthday parties, and pregnancy, but also the bad ones.
3. As I mentioned in the previous point, people mostly lie, so they do not get in trouble (mainly kids).
4. Not all lies are equal. I think, that if the reason for lying is good, then it is justified. On the other hand, when I want to do something wrong by lying, it is bad. But all lies have their cost, like losing the trust of other people.