Reminds me of the guy who bought a new Winnibago, put it on cruise control and went back to get a coffee.
When it crashed, he sued the company .... and won!
Evidently, this was a true story ....
Sorry, I have a strange compulsion that whenever I see "... true story ..." written on a web site, I immediately look up the story on the Urban legends sites and am compelled to post the results. I really don't understand this compulsion, since normally I never let the truth get in the way of a good story, but ...
The general case is too generic to prove or disprove ("some guy", "the company", no date, etc.). See http://www.snopes.com/autos/techno/cruise.asp
for discussion of the genre. A common specific case (Mr. Gransinski in November 2000) is reported to be false here: http://www.snopes.com/legal/lawsuits.asp
Of course, I don't actually verify the stuff that Snopes claims to verify, so for all I know, they could be making all their research up just like the rest of the Internet.
To get back on the topic of dismounting only after stopping, in my experience even if you wait for the bike to stop before getting off, there can still be problems.
1) I've stopped, put my right foot down in a puddle of oil, and then had my passenger jump off (literally jumping off the right passenger footpeg). My foot went flying, and the bike got some new scratches.
2) I stopped at a gas station after at least 13 hours of hard riding. I didn't realize my leg was almost entirely asleep from the vibration until I tried to put the weight of me and the bike on it. I did manage to keep it upright, but it was a close miss.