It's also interesting to note that Canon doubled (or more, depending which older camera you compare it to) the shutter life in their new flagship SLR by using carbon fiber instead of metal in the shutter. That thing that slams around at extremely high speed to pull off 1/8,000th second exposures. Metal just doesn't stand up as well.

It's one of the heaviest cameras they make, so that's not why they used a carbon shutter.

The shutter is usually the first thing to fail on a digital SLR. Mine is rated to about 120,000 actuations.