According to this USA Today article, a growing number of medical groups are insisting on holding their meetings only in cities and states with "smoke-free air" laws. A snip:
The American Public Health Association, which adopted a smoke-free
Yet most of the largest, including those of the American Heart Association and the American Medical Association, don't select convention cities based on smoking policies. Heart association spokeswoman Kim Becker commends the NCI for its decision and says her group considers smoke-free legislation when selecting locations for meetings. But Becker says her group already faces severe limitations when selecting a city for its annual scientific meeting, which attracts about 27,000 people. Only a few cities can handle a convention that size, Becker says.
I'm guessing that this will become less of a problem as more and more cities and states are adopting smoking bans. This also should make Marriott more popular with medical groups, I would think, since the chain will go smoke-free in its U.S. and Canadian hotels as of September. (Westin went smoke-free in its U.S., Canadian, and Caribbean properties in January.)