Hui and El Toro,
I agree, running in protocols are from an earlier time when metal, casting and machining technology was not as good as it is today, now, warm them up gently then go hard.
Those who disagree, I'm happy to be wrong but tell me about your experience, not a friends experience or something you've heard, your personal experience. I've had over 40 new bikes and cars plus plenty of rebuilt engines, treated them all this way and never had a problem. Race engines in particular, I would rebuild them, start, warm up, if it ran well shut it down until the race, probably a total run in of 10 minutes, never had an engine failure, plenty of rider / driver failures though.
Maybe I was a better mechanic than rider / driver.