jmr - that is a severe, and fortunately very unlikely, worst-case scenario. the macro market is unquestionably overvalued and some areas will experience a lengthy plateau of prices (read: now) followed by a moderate price reduction of approximately 10% in NYC that will occur over the next few years. the reduction will be higher in some areas such as South Florida, San Diego, Boston, Vegas, etc.
the truth is that while inventories are rising, the marketing period to sell a unit is only approximately 150 days - in other words, its back to its normal level of 5 years ago before the irrational buying spree. there's still nothing to get TOO worried about as selling time is at its traditional norm and prices are still rising (albeit in the single digits now). further, the NYC market is rather impervious to the fluctuations we can expect to see in the markets mentioned above as NYC has a reversed renter-ownership ratio compared to the rest of hte nation, thus always maintaining a huge glut of people looking to move from renter to owner. in short, don't worry too much about a bubble in NYC.
in light of the above, watch what happens to Brooklyn, Jersey, et al, when the market does begin to push downwards. the classic supply-demand practice will come to play - are you going to buy in brooklyn or NYC if you have the choice? in other words, if you're thinking of buying in brooklyn, you're probably better renewing your lease for another year or two and getting a lot more for your dough in '08.
just one guy's thoughts...