Why does the "Mouse" preferences GUI not allow me to enable two-finger scrolling?

Press Alt+F2, write gconf-editor, it will open gconf-editor, go to destkop, gnome, peripherals, touchpad and type 2 for the variable "scroll_method". The option will stay grayed but two finger scroll will be enable. Works for me.

This is my understanding of it. Ubuntu doesn't have support for the Synaptics touchpad officially out of the box, so what that script does is it emulates the multi-touch. I think. I don't know for sure, but that is my understanding of that. (I myself have a Synapatics trackpad on my Asus Eee PC, so I've spent a far amount of time working on this.)

I don't have a laptop to test it with, but I recently stumbled upon this site: http://stuffivelearned.org/doku.php?id=os:linux:general:synapticstouchtricks

Perhaps this helps you.