Unfortunately, the "stay in the middle of the room" strategy doesn't work for all dances. If you're in a venue where people dance international foxtrot, everyone is going to converge on the center about three measures into the dance. Most people will dance from the corners in towards the center, and then back out to the corners, on each long side. In quickstep, the open level dancers frequently go to the center to do their hoppy-boppy stuff, then zoom back out to the corners. In either of these dances, beginners will probably be less likely to be run down by keeping to the edges around the long sides, although no place on the floor is really free of other dancers.