I haven't watched the Extreme Coupon show yet, but from what I've heard, it seems like most of the things bought are for pure effect. I would hope that these people are donating a majority of the items to family, friends, food bank, etc.
I will only "stockpile" things when they are free or nearly free, and only if it's something we can use.
As for me, I currently have a huge stockpile of diapers and baby wipes in my basement. My daughter is almost 1, and I probably have enough diapers and wipes to last her for a full year. I did get all of these for nearly free though. If I were paying full price, I'd just buy 1 months worth at a time because they take up so much space.
I have enough TP, paper towels, and Kleenex for about 3 months. I didn't get a phenomenal deal on them, but I hate to run out of those items. I can sometimes get toothpaste and toothbrushes for free at CVS, so I have about 6 months of toothpaste and about 20 toothbrushes. I also stock up on antiperspirant anytime I can get it for free, or almost free. I probably have about 6 months of canned items, mostly because I hate to run out of staple items. I limit frozen stuff to a 3 month supply, which usually coincides well with sales.