I bought DVC to enjoy WDW and the exchanges (have yet to do any) and stay at high quality accommodations. Since I did so early in the program, there is no doubt that I have recouped my "investment" and I use that term loosely; it is still primarily a vacation destination.
But, after the purchase, there are the yearly maintenance fees and for those who borrowed, a mortgage. If many buyers have a primary home mortgage, car payment (maybe more than one), any credit card debt, college tuition, etc., it may be that should things slow down significantly, DVC may be more of an expendable expenditure. If enough people feel a "pinch", there goes the secondary market.
This sounds somewhat like the stock market mantra of the 90's; it's a new paradigm. Well, my 401K looks like, well, let's just say "OUCH"! Should the pension plans have the kind of losses that begin to affect retirement payouts, people may really panic and sell their stocks. And these aren't JUST internet companies who don't make money. JNJ has lost around $25 from its year high. That's a chunk of change. Daddy always said, "A bird in the hand was worth two in the bush" and I've read articles lately where the interviewees have concerns that we are headed for a significant slowdown. Look at Japan and how the market remains in the dumper there after, what, 12 or more years. NASDAG is down about 66% off its high. Worldcom's about to declare bankruptcy. Who's got them financed???? I think there's a legitimate concern about things that people should at the very least consider how serious this could be.