Yes, I agree that it could have been a disaster if it had hit someone...but it didn't...thankfully. I don't follow this stuff all that close, but I don't think this is a common occurrence whatsoever. If it were, we'd hear about it a lot more. Anyone know when the last time it actually did happen (being sincere, I really don't know)? Again, not saying it wasn't bad, it wasn't potentially dangerous, etc...it was all of those things. But from my understanding it was a completely random, freak accident that almost never happens. If pieces were falling off every week or every month, I'd probably feel different.
Wasn't there just a bus crash not all that long ago, full of students? Why no fear that WDW buses are unsafe? How many of them crash every year? I'd bet it's a lot more than monorail pieces falling off or someone getting hurt on them. Being someone who stays offsite and drives in, we see/deal with lots of buses daily. On one hand, I feel sorry for those bus drivers, as they have to deal with tourists who cut lanes, slam on the brakes, etc... But at the same time, I've seen some very, very questionable driving by the buses...repeatedly.
Me personally, I'd feel far, far safer on the monorail than I would a bus. I could be wrong, like I said, I don't monitor this stuff super close. Monorails are ancient, but just IMO, far from unsafe. One piece falling from one for the first time in who knows how long, doesn't make them "unsafe" to me.