I would love to know what your definition of "stupid reasons" is. Why shouldn't I be able to use my computer - the way I want to, as is advertised - without it slowing down/crashing/generally behaving strangely?
You seem to think that there are a lot of PC users who have bought Macs as a result of messing around with their registry and wrecking it. Whilst there may be some, this is a very very niche thing. And you have to ask yourself, why would anyone want to fiddle with the registry? Usually because its messed up. And don't say that it is because they were doing "stupid things" because it is very well known that registry files become corrupt for reasons totally unrelated to user intervention. And there is no simple way of fixing these things unless you are very clever or very lucky. AND for many windows problems, the fix-it-yourself solution presented on the Microsoft website invites you to fiddle with the registry. Of course they give you the appropriate health warnings but can you blame people for trying to fix their computers the way MS advises?
The kind of user you are describing does not fit the demographic of the user who tends to purchase Apple products. In general, the Apple market is post-secondary educated, affluent and to a large degree, female. Not exactly the high school kid doing "stupid things" with his computer in his bedroom upstairs.
As far as things that have gone wrong. I had a kernel panic once which I tracked down to my Norton Antivirus software. Getting rid of it solved that, and I haven't had that problem in the two years since (and haven't had a virus problem either). I sometimes have trouble getting the computer to connect to my wireless network when it wakes from sleep mode but only the imac not the laptop. Solution, I just keep it on all the time, which is how unix based systems like to be anyway, as they are default scheduled to do system maintenance at night. Although I admit I would like to get that one solved. And occasionally when there is a major operating system update I have to delete and reinstall my printer as it doesn't get recognised.
And that's about it. Really. Would you like me to share my PC experiences with you? I'll need a few hours to write it all down.