How many sets of dlp-link glasses can be used at one time?

As many people as you can fit in the room in front of the your TV. DLP Link is a line of sight technology where a flash from the set is used to sync the glasses. So, you are only limited by space and the distance the DLP Link can travel and still be read (on mine about 10'). Make sense?

There is no decent way of answering this without doing some actual tests. Just get one pair of glasses and go to the location in question. Turn on the projector (I assume) and activate the 3D mode. Go to the far left seat, sit down, and see if the glasses work. Do the same to the far right seat. Go anywhere in the room, sit down, and look at the screen. If the glasses work than they will work when the room is full of others wearing them as well. This way you don't have to buy 80 sets of glasses to know if it will work. Otherwise I would be guessing. It depends on the quality of the lighting in the room, the projector used, and the glasses. It may work fine for one person in their environment using their equipment, but not for someone else using other equipment in a different room.