I rebuilt an ST3 engine a couple of weeks ago due to a bad main bearing. I didn't video that one beforehand, but I do have a little video that shows the noise they make well.
The bike in the video is an M400 with 22,000km on it. The owner had bought it in a private sale, been on several rides with his mates, and was generally happy with his bike. It wasn't until he took it to someone for a service that he first heard the phrase "WTF is wrong with that!" A bit shocked by this, he then headed to Ducati City at the recommendation of the someone to see what they thought. They too asked "WTF is wrong with that!" Because Ducati City won't deal with the grey import bikes, they sent him to me. I heard it pull up out the front, with the noise making my skin crawl so badly I had to go out and turn it off. The high idle wasn't helping the horrid noise either. This is what it sounded like.
Luckily for the owner, I found Michael at AdrenalinPB had a second hand engine. We popped that in, and all was happy again.
The ST3 I mentioned at the start was in for a service, and when I fired it up afterwards I had a feeling it was noisy. It had around 42,000km on it, and 1,500km later it had gone from a bit of a noise to what the video shows (it might have been a bit worse). It took about $6,500 (including some Pistal high comps and a head reco) to make it quiet again.
I had an S4 Monster in for some work last week, and when I fired it up I heard the dreaded noise again. It had around 15,000km on it.
I've heard of quite a few MTS1200 doing it around the 20,000km mark. This is a bit surprising as the 1198 or Diavel don't do it, and theoretically they're all the same thing bottom end and production wise.
The cause is usually the inner race of the RH main bearing pitting. Sometimes the balls and then the outer race pit as well. I guess it might depend on how long you let the noise run for as to how far the damage travels.