Yeah, I know.....but that is:
1. Slow. Much slower than a page down key.
2. Uncomfortable (for me). I almost always have my edge in landscape mode when browsing (or using docs2go) and have a keyboard plugged in. Hands on the keyboard, it is not natural - and takes a lot of effort (don't laugh, I'm lazy) - to reach up and use the trackball. Just doesn't seem like it should be necessary to do that.