Parallax scrolling is one of the big design trends online at the moment, there are some really great examples of it online. Now building on this idea, more and more one-page websites are doing this cool effect where by the page stays fixed, and while you scroll animation happens to advertise a project or similar (see the new site for the Mac Pro as an example). Nine times out of ten it looks really good, however I just find them frustrating because it changes a standard behaviour into something new and unexpected.
I am glad I am not alone in this feeling: Trent Walton posted a wonderful short piece about 'scroll hijacking' a couple of days ago, where he also moans about how 'experiences shouldn't dramatically change how basic input devices operate.'
While experimenting and introducing new this is good, it is also vital that things work as people expect them to. The best bits of design should not need to be explained, affordance is important.