DISCLAIMER: This is one of those questions where you are going to get a ton of opinion and speculation, and my reply will have some of that in it as well.
I think there is a lot of myth out there about what cars actually need to maintain them as they are and should be. For instance, your comment about the M5 owner. The entire statement is about seat of the pants performance check. It could be that the driver was very excited, still hyped on adrenalin, and it felt better to him because he felt better. On the other hand there is some basis of truth, depending on the driving habits of the individual involved.
It is good for any vehicle to be driven for an extended period of time. If the engine and components are not given a chance to warm up thoroughly, you'll find that carbon build-up and moisture will be left behind where you really don't want it to occur (in the oil and crank case most notably). Does this mean you need to once in a while drive the performance vehicle like a raped banshee to "clean the carbon out"? Not at all. If the car is ran up to operating temperature on a regular basis (a minimum of once a month) and driven for a good set of miles (30+), you should have no issue with the car other than normal maintenance and should expect the vehicle to perform when you want it to perform.
Even if it were true, what would be the maintenance interval and specifications for an "Italian Tuneup"? Do you roast the rear tires once a month? Twice a month? Is driving at 150mph what needs to happen? And for how long? What should you do to achieve this "blowing out the carbon" and getting your high performance sports car to a proper tune? I hope you see the problem with this, because there isn't any correct answer. It all comes from seat of the pants tuning, which isn't accurate, to say the least. People will tell you this must be done so as to give themselves a reason to drive their vehicle to the extreme of their vehicle's ability. This is one of the two reasons to have bought the vehicle in the first place (the other reason is for the bragging rights). Something you'll find, though, is owners of these higher performance vehicles are not content with "normal driving". It is way too easy and exhibits way too much fun to be able to drive such a car at the performance level it was designed. This is the reason you purchase something like this in the first place. Most owners of such vehicles will give it the Italian Tuneup on a regular basis, just because they can.
What it boils down to is this: Give me some empirical evidence an "Italian Tuneup" is needed to maintain the proper running of a vehicle and I'll believe it. Until then, I'll stick with what I know, which is, proper maintenance and regular driving is all you need and the vehicle, no matter what vehicle, will be just fine.