I am using ICS android phone.
I can see pointer speed menu, at Settings > Language & input > MOUSE/TRACKPAD.
Is this menu necessary? why do we need this menu?
There are tablets such as the Asus Transformer, operate in dual mode (as a tablet and like a latop when docked). In the docked mode, they display a mouse pointer similar to a laptop and are controlled by a Trackpad. This menu is for controlling the sensitivity of the mouse pointer in those devices.