Cleaning the Mac Mighty Mouse

They do get clogged up. That's the only pain with them - they weren't designed to be cleaned and Apple didn't expected them to get clogged with gunk.
Years of scrolling down and not able to scroll up ensued.

How to Clean - attempt ONE.

1. turn the mouse upside down
2. Put the ball on a sheet of white paper and quickly move the mouse around for a minute or so making sure the ball is being exercised.

This sort of works sometimes. Though often just as a brief respite.

How to Clean - attempt TWO.
When it's all got too much and attempt one isn't enough then:

Tools needed are few, I used the screwdriver of a Swiss Army knife and a tiny phillips screw driver and glue to put it back together.

There are 4 tiny rollers in the ball device. When you take the device apart make a note of their orientation. You can review it in the video.

How to do it, see this helpful Video.