In order:

1) Just because something is obvious doesn't mean it shouldn't be researched. For instance, for a long time it was obvious that light things fall slower than heavy things.

2) I'm not sure what you mean by "really required". In the literal sense, no research is "really required". In the non-literal sense, it's better to have data about something than to not have data about it.

3) I'm not entirely certain why whether you find the results interesting or not is something the researchers should take into account. What's more, adding more independent variables to the experiment would complicate things unnecessarily.

It was beyond a doubt to my mum and almost all women everywhere that cracking your knuckles led to arthritis, it was beyond a doubt. Except it doesn't, there's not even a hint of a link between the two.

Just because something seems obvious, doesn't mean its right or that the science behind it won't lead to something more interesting.

I agree that some data is better than no data, but I think these researchers' time and money could be put to a better use.

And sure common sense sometimes is wrong and it must be corrected, but I don't think this case was a priority.

On Richard Feynman and spinning plates, from http://worldandi.misto.cz/_MAIL_/feynman.html :

"He challenged himself to describe in equations the wobbling movement of a spinning plate being tossed in the air by a student in a Cornell cafeteria. After much effort, he was able to show that, consistent with his observations, for a small degree of wobble, a one-to-two ratio between the wobble and spin was indeed valid. When Feynman excitedly described his results to Bethe, the other scientist listened with interest but wanted to know their practical value. [...] Ironically, he found that the spinning-plate movement he had studied just for fun also had application to the electron-spin problem."

It's about creating an accurate model of the world and universe. I never saw the point of being caustic against any kind of research.

It does not seem that obvious to me. Yes men will try to impress women but why do they seem to do it with risky behavior? One may suggest that it may be better evolution wise to try to impress women with steady and dependable behavior. (It turns out you can only impress their mothers this way.)