What Apple (and most others) called a "desktop" was a box that was took up an awful lot of that very thing. Most people put their monitor on top of that box, even if the box wasn't strong enough!
So the manufacturers got tired of having those beige boxes destroying any kind of style or cleanness of a desk and put all that inside stuff in a vertical box and called them "towers." Of course, that immediately brought to mind "power" something that all manufacturers fought about for years... It's only thanks to the ever decreasing size of electronics that we didn't end up with "desks" that only had support on one end! The other end would be supported by the humonginormous "tower!"
I think Apple is at a cross road with the mini and Apple TV. Neither has developed into a big seller, their almost identical in (possible) capabilities and they are still too limited and costly.
The mini is nothing more than a laptop without a handle, all its parts are of that heritage. So there's no reason it couldn't be as powerful as any of the laptop they make. But they love to keep that profit rolling in, so don't expect them to do anything that they can't see as a net gain in that.
That's my theory, anyway...
