Chicago Office Tower to Go Condo?

Crain's Chicago Business reports:

The owner of the landmark IBM Building is considering joining the growing ranks of downtown office buildings that are converting in whole or in part to residential condominiums.

After losing its two largest tenants, and with the office market in a deep slump, landlord Prime Group Realty Trust would likely find it easier to sell condos than lease commercial space in the 52-story tower, one of famed architect Ludwig Mies van der Rohe's most celebrated buildings. The high-rise is 32% vacant after the departure of IBM Corp. Law firm Jenner & Block LLP, which leases 22% of the building, moves out in 2010.

This is a huge trend in some old cities.As jobs evaporate in downtown areas what are they going to do with all those office towers?