I have had to make the call to reactivate my XP install, this even when I first used the CD freshly un-wrapped from the package it came in from the pc builder.
Then after a pc cleaning in which I removed my video cards to clean out dust and reinstalled them, this was considered a major hardware change, didn't change a thing just removed and replaced the same hardware but that was enough to warrant a call to MS. No issues really just a 5 minute call and I was up and running again.
I have no problem calling to reactivate something I bought, I also have no problem with being limited to how many pcs i can use the software on at one time.
I buy a program I want to install on 3 home PC's + my laptop for fun? It's ABNORMAL to use one PC today - many of us have 5 or six placed around...
This may be true but you bought a license to use the software on one computer at a time, the EULA states specifically in section 6 you can make a back up to be used for reinstalling the software and in section 8 you can transfer the software to any other device if you uninstall from the other, there is no limitation as to how many pcs you can install it on, but you can use it only on one pc at a time. this is really no different than most other software.
A major hardware change is no exception, that major hardware change could be your buddies pc for all they know, it is impossible for them to say whether that change took place on your machine or someone else's.
Actually makes sense to only be able to run it from one computer at a time, this is what prevents piracy, yes the second pc may be yours but then again it may be your neighbors or the buddy down the street and this is why the one pc at a time
Common sense and real simple to understand. Read the EULA, MS makes theirs pretty simple to understand, and I see them doing nothing wrong with preventing you buying the license and then installing it on all the pcs you want be them yours or you friends, simple as that.
By using the software, you accept these terms. If you do not accept them, do not use the software. Instead, return it to the retailer for a refund or credit.
There you have it, right there when your installing it, don't like it take it back and get your money back

BTW if your retailer won't give your money back there is a contact for MS and they will

I think people seem to take EULAS as a joke and few ever read them, when that is all they need to do to understand exactly what they can or can not do with their software.