While you raise an interesting point, I believe this change was made as heavily requested by the iTunes user base.
Allowing only 3 computers to be authorized is simply not good enough. We have 4 computers in our house so one wouldn't work with this scheme. I think 5 is much better.
I don't see this as anything but a big improvement for the honest user. That to me is what Apple is trying to achieve here. I hope it ain't stable. I hope Apple keeps making changes like this that improve the use of iTunes.
Just my two cents. Enjoyed reading yours.
Not Good: Jobs Changes The iTunes Rules