While the might mouse is very stylish looking and an effective tool, it does have an Achilles heel; the scroll wheel is very small and this seems to make it more prone to getting gummed-up and it then leads to it no longer working. If the scroll wheel on your mighty mouse is no longer working, here's what I've done to get mine working again.

Unplug the mighty mouse from you computer. Turn you mighty mouse upside down. Get an alcohol pad and then rub the pad on the scroll wheel for several minutes. You want to push hard enough so that the scroll wheel is scrolling and you want it pushed into the mouse. After several minutes of this, get a can of compressed air and, while still holding the mighty mouse upside down, spray the air into the gap around the scroll wheel. Make sure the scroll wheel is moving around and pressed in while you are doing this.

I've had to go through this procedure every several months, but it has kept the scroll wheel working on my might mouse.