Where does this number come from?
The DPReview press relases and reviews of the various models don't list the number of cycles the shutter is rated for. Canon's website doesn't include it under "specificatons"; the 7D has it under features, but i can't find numbers for the 20D, 30D, 40D, or 50D.
There's a few websites (like steve's digicams, digitalcamerareview, and batteries-wiki) that copy the Canon press release and list a 100,000 cycle number at the end, but I'm trying to do a presentation, and I would prefer to rely on Canon's official mouth (particularly for the 20D and the Rebel line), not on these websites.
Note: the DP Review news article on the 30D appears to be the only press release of its kind to mention the cycle life; the 20D and the 500D don't mention it.