The DVD region coding came about during an argument of technology control by 
several large companies, some time back.  The initial premise was to use the 
"shared tech" principle established with CDs to avoid something akin to the 
videotape VHS/Beta war that severely screwed that whole industry for a time 
(still, the break between the formats used professionally and by the average 
person tends to leave a rift in quality that could be closed by uniting the 
formats or scrapping both in favor of something universal).  Unfortunately, 
Sony had a good deal of money invested in certain things they had developed 
and did not want to give up, things that were inherent in the way their 
machines dealt with DVDs.  This would have also made more easily available 
the read/write type of machine, as well as numerous pretty functions that we 
may not see for years to come, now.  The initial break-up into regions was 
intended to give certain companies a greater reach in different areas, 
focusing on where they thought their primary audience was going to be.  
Luckily, there was originally going to be many more regions than the 
(relative) few we have to suffer through currently, but initial market 
testing proved most folks unhappy (I'd use worse language, but, well, it does 
sort of boil down to unkind ways of saying unhappy) with the way they were 
working things.  The region coding is not the only locks placed on DVDs, 
however, there are a number of others used in special instances, including 
one to blank out the screen and sound (though, not always both) if the 
machine is running through another recording device (don't ask me how it 
knows, it just bloody does).
        As far as the self-destructing CD thing goes, why do you think they 
made them un-cased and totally breakable?  The original idea was, they'd be 
so cheap it would ruin the industry once they replaced audiotape (this being 
way the hell back, nearly the seventies, when people thought of CDs as some 
for the future), so they were designed in a way that it was likely they'd be 
busted, scratched, or what have you, and have to be replaced.  Some companies 
have, in the last few years, started making their CDs stronger actually, but 
this is rare, and more often we're getting weaker materials, and cheaper 
recordings.  Most of the cheap and crappy stuff is being done right here in 
the States, whereas the strengthening (and some sweet redesigning of the 
methods for recording and the technology used therein) is coming from 
elsewhere, mostly Asia and the far western part of Europe.  Oh, and if you go 
super, super cheap, you can find the destructable CDs that literally melt 
themselves after being played too often.  First time a friend of mine got one 
of those and it did that, it scared the crap out of him (fun to watch; bad 
position to be in).