FRP notwithstanding, the comment about UIs is important in that OOP was originally developed around the needs of user interface components with their inherent "mutable state" and single-threadedness (ever find yourself needing to use two mice at once?)
> (ever find yourself needing to use two mice at once?)
Yes. I tried to get that working in GNOME once, naively expecting that because it's trivially easy to state well-defined behavior for multiple mouse cursors, it must also be possible to have multiple mouse cursors. But no. I'm still bitter that this seemingly obvious concept seems to be so thoroughly precluded at very basic levels.
I would love two nice for pair programming. Also for playing/making a first person shooter for two people where each player controls one arm/gun. A third player would control the legs and head. It would be amazing!
Aside from the more obscure use cases in sibling comments, multitouch implies potentially having a large number of "pointers" at once. Usually combined to make a single gesture, but the OS is supposed to do the right thing if the user tries to scroll multiple views at the same time or whatnot.
