As AMD gets more and more popular, a greater number of people do extreme overclocking. The new HSFs get larger and more popular. Every overclocker's worst fear is crushing that brand new AXIA chip or cooking that sweet Blue Core. CPUfx came out with the copper shim which was a big hit for those who like to play it safe. The old copper shims were conductive, while that isn't a surprise, its also kinda scary to the person who checks everything twice.
Shims come close enough to the components of the processor that they can short the processor out.
An added bonus is that these shims also work on Intel or AMD, as do the DTS-400 shims. 11373 hits on this page.