Good point. I guess I've grown accustomed to random things on the page stealing scrolling functionality (e.g. Flash/plugins, which I've disabled now) so I usually don't try to scroll unless the mouse is on the background somewhere.
Yes! Me too. Same with focus - I often find myself subconsciously clicking the background of a page to defocus whatever the page's developer or browser has decided should be focused. Flash is definitely (or at least used to be) the worst offender.
