Back in the 1980's when I was a kid, I was in Yosemite and witnessed a rockfall off of El Capitan. It was nowhere as big in size as the post that initially started this discussion, but it was big enough to cause a thunderous roar and a rather large dust plume. It was an experience I'll never forget.
I also witnessed two rockfalls while hiking in the Morgan Pass area (close to Rock Creek). Scary at how it happened after I had been underneath the area about half hour before it happened.