Luxury Developments with empty halls

Are your neighbors never home? Are your building's beautiful amenities barely used? I'm a reporter with the New York Observer and I'm writing a story about luxury developments that have a large number of unoccupied units that were purchased as investments or pied-a-terres. In other words, I'm looking for co-ops or condos that are technically "occupied" and off the market, but that are basically sitting empty. If you live in such a building and would be willing to speak with me about it (or have any other tips or ideas about the phenomenon, please send me an email at kvelsey@observer.com.