Hi,
First, let me caveat this request with the following statement: I've never used SE, but I'd be interested in it if it allowed the user to assign keyboard hotkeys to rocker gestures. Rocker gestures are discussed here. Essentially, it allows one to use different mouse button press sequences to cause an application to do something. I think Opera was the first browser to include this capability in it's web browser. I'm sure that other apps have followed suite (I know Avant Browser has). I'd love to assign "backwards" and "forwards" rocker gestures to a particular source code editor I use (Source Insight) and a few other programs.
In particular, I find rocker gestures much more handy than mouse gestures because there's no interpretation of how you draw using the mouse to fool--essentially, it's like having digital as opposed to analog: there are very discrete steps that can't be confused.