I glued down a bamboo floor on a concrete slab in my house in Florida. The glue was about $1/sq ft, so it's not cheap. This particular glue was especially expensive because it had to form the vapor barrier as well as hold the floor down. It worked great and I loved the finished result, but if I'd had the option of nailing, I would have done that.
Some reasons:
It's often much easier to cut oddly shaped pieces (i.e. around doorways) when the adjacent pieces are already in place. Gluing makes this difficult because you only have a short time to get the pieces in place once the glue is applied. You pretty much have to have everything cut just right before putting the glue down. Also, it's much easier to cut the oddly shaped pieces using trial and error. Once the glue is down, you don't have the option of putting the piece in place, then removing and recutting it. It's all covered with glue and you don't want it anywhere near your saw.
Also, the glue gets in your way. If you lay down the glue for four or five courses, you have to reach over it and not put your hands or elbows or knees or feet or forehead in it. It makes for a sore back (not that nailing will improve that situation much). By the time I finished I had glue all through my arm and leg hair. That was pleasant to remove.
The glue smells terrible, and is harmful to breathe. Even with a respirator, you have to have adequate ventilation. If you're in a cold climate, you don't want to do this in the winter.
If you ever have to repair a piece of the floor, it's much easier to take out a piece that was nailed than a piece which is glued. The glue I used will pull up concrete with it if you try to take it off. I'm sure it would do the same to a plywood subfloor.
If you're interested in seeing my results check out the pictures at this link:
formatting link
Josh