Matt - I admit ignorance on the S/L crisis, but a guy who knows a lot about it claims the tax shelter schemes of the early 80's played a major role.
As I understand it, at the time the depreciation rates were much higher on real property, and over a shorter time period. This was coupled with very high maximum tax rates and the difference in rates between ordinary income and capital gains.
The idea was to get financially ignorant people with lots of taxable income (doctors, actors, etc.) -- form partnerships and buy depreciable property and take the depreciation against ordinary income. At 10% they could buy a million dollar building and take 100k depreciation a year, reducing the doctor's AGI by that much.
Few years later sell it to the greater fool, and the difference between the depreciated building basis and the sale price was taxed at capital gains rates - so you not only defer the tax for the ownership time, but you convert the tax and make the spread between capital gain and ordinary income rates, which was much higher then. This also drives the prices up artificially, because a more expensive building just means more depreciation and more tax deferral - there was an incentive to pay more. And there's general speculation by the public adding to price appreciation, like today.
Then comes Congress with the TRA of 86 - changed the depreciation amounts and periods, hobby loss rule, and recapture provisions to kill these shelters -- all of a sudden the schemes don't work anymore. Add into that that a lot of the financing was no-recourse (lender can only look to the property) -- without the shelter demand market prices collapsed, and you have a bunch of properties worth a whole lot less than the outstanding mortgage.
If the mortgage is no-recourse, what does the owner do? - walk away from the property and let the lender figure it out....
(until congress shifts the burden to John Q. Taxpayer, who has to come in and bail out the industry!)