I don't really see a problem with the light-heartedness but if I am working on a project and I need to find an answer so that I can move on, it might be a little annoying to read that joke before getting to the answer. As a community, joking will make us closer but Stack Exchange as a tool for information would not welcome it. Think Wikipedia or a dictionary. We use those tools to learn and find information.
Unlike Wikipedia or a dictionary, Stack Exchange is answered by individuals. We aren't collaborating to find the best-worded and most complete answer. When people look at Wikipedia articles, "Wikipedia" is an entity that is speaking. We don't expect "Wikipedia" to make jokes. However, when people look at Stack Exchange answers, we are fully conscious that it is a single person adding input. But at the same time, if editing becomes more intense and people continually improve on the answer, the "Wikipedia"-like quality starts to show.
So it could really go both ways depending on what we choose to make of this site. I think it is important to keep in mind that we are humans interacting with humans, and at least for now we should allow a bit of fun.