I have done 3 Full Body workouts in a week however, i was doing high rep/low weight workouts. It worked well for me.
There's no 'rule' against it, but it would be hard to do three heavy-weight full-body workouts in a week, and some people need more recovery time, so couldn't fit in 3 in a week.. I believe your not suppose to do 3 full body workouts a week does anybody know why?