I was at a home yesterday that had 2 return vents and ONE supply in a
bedroom! Now, the house has been going through some remodeling (for the past
6 years!) and it may have been 2 different rooms turned into one. Returns in
the floor and supplies in the ceiling. Not a very good setup.....

Not as bad as you might think, though. With the returns in the floor, you suck

the cold air out, and the warm air moves more or less uniformly down to
fill the remaining space. If you do it the other way, you get more turbulence,
and
the air coming out of the duct can go straight up, without dispersing, and get
sucked
out the return vent without ever warming the room.

--Goedjn