Do they just randomly expand or what? If its in copper they probably are expanding without knowing enough about what their opponent has, or they know what their opponent has but dont know what it means. The build you describe uses a TON of gas and must take a really long time to build up so there is no reason they wouldnt be able to hold the expansion if they have been using it properly and have detection of some kind. I mean, dark shrine alone takes a long time to get up, but to get charge researched as well as 4-6 DT's...
But... yea... in lower leagues I can see expanding even more risky since you may not have the experience or knowledge necessary to make a judgment on if you can safely expand or not. I consider myself fairly decent and I still misjudge expansion timings sometimes.
Interesting to note that somebody suggested making it HARDER to expand somewhat recently, because they felt it was too easy and too powerful when you get one running :P
http://sclegacy.com/forums/showthread.php?t=3920