Comment 25 for bug 951123

And someone reported it upstream, actually two people.
https://bugzilla.gnome.org/show_bug.cgi?id=675047

https://bugzilla.gnome.org/show_bug.cgi?id=674716 which interestingly reads, but it seems this fix is for trackpads only, and not mice.
"So, the command to play around with for xi2.2 is

xinput set-prop <deviceid> "Synaptics Scrolling Distance" -<vert> -<horiz>

to find good values for vert and horiz, look at the current values with
xinput list-props <deviceid>

Note that this only works with the synaptics driver currently, and only with
version 1.6 (or 1.5.99.something)."

Also note that the interia calculation in the driver seems to be broken for
negative deltas, so you'll have to set "Synaptics Coasting Speed" to 0 0 for
now, or else you'll get 'infinite scrolling'."

For more details, http://arstechnica.com/civis/viewtopic.php?f=16&p=22816149

Also read
http://cgit.freedesktop.org/xorg/driver/xf86-input-synaptics/commit/?id=1874094f0e99d8db319f6cf769ce5a25c9bc490c
and
http://who-t.blogspot.com.au/2011/09/natural-scrolling-in-synaptics-driver.html