Interesting discussion. About a month ago I bought a "like new" magic mouse from a guy on eBay. Maybe a week or so later I started to get erratic window behaviors that wouldn't scroll and when they did they ran wild. Did some tweeking with disk utility and TechTool Pro and things seemed to settle down, A couple weeks ago I decided to configure the mouse for other tasks and my computer went out of my control opening windows and typing a single keystroke dozens of times. Lost complete control of the magic mouse utility and finally managed to boot from a disc and run disk utility, which, itself, was behaving oddly.
To make a long story short the mouse, even though I restored it to the old configuration, still ran wild and disc utility gave me red notifications to repair the hard drive. I retired the mouse and reinstalled my old wireless mouse and all is well. It would appear the magic mouse is the source of unmanageable problems.
Now, I hope eBay and PayPal will fulfill their guarantees.