Yeah, the video player ended up being a so-so example. :)

The point is that it's common to have UI elements that can go one way or the other and it's often possible to justify either way.

As far as why there's a lot of experimentation, I think it's just because designers are trying to find the pattern that will make people go "wow, look at this, this is so cool/smart". Look for example at the praise Loren Brichter got for pull-to-refresh. (it was indeed cool and smart) I think a lot of people are experimenting to see if they can find the same kind of pattern that end up sprouting all over the place. I don't know if this is really something new though.