I am not so sure its the recession, most 911 owners I know have plenty of €'s stuffed under the mattress to last a couple of years more of the recession. Ok a few of the chancers who made a few quid with Celtic tiger enterprises company's (construction, renewable's, high value products etc) have ditched their cars.
I would go with Mac's theory, its crazy how a perfect condition 80's+ car is worth half the value of a pre 79 even when the condition could sometimes be described as ropey for some of them especially merc's for some reason.