Well, firstly you are a bit of a legend, not just for doing 70k on your M2, but also for checking your oil pump gear at service time. Not many people will have done that...
But back to your question, another forum member, who has seen a lot of HDs, and I were discussing this at a recent get-together. He has seen a number of Buell engines lunched like this but no Sportsters, which interestingly use the same gear. He thought that was cos Buells were used harder...
I always thought it was a bad batch of gears, cos the failures appeared to happen on 03/04 models (I have an engine that failed after around 10k), but more recently there has been at least one failure on a tuber. However looking back, I got some M2 bits off a guy who was breaking his, and his engine lunched cos of the oil pump gear after less than 7000 miles, back in 2001.
Buell introduced a revised gear in 2006, which as Maz points out, was designed for their race bike (pre-XBRR which had a revised oil pump).
My gear out of my Firebolt showed some wear, it was probably nothing major and would probably have lasted many years, but when you think your engine could be destroyed because of the the weakness of this one component, it makes sense to put something more robust in.
Not really answered your question, but preventative maintenance is better than a lunched engine.
will be along in a minute to put me right...