My friends play with a Switch Clause because it's really cheap if I switch out a Machamp and switch in Alakazam on a Psychic, not realizing how vital this is to the game.
Lolz... worst. clause. EVAR.
Before I got into the competitive scene, I knew a lot of kids that played the "no legendaries" rule and that was it. Everything else was fair game to them and yes, a lot of them carried Sleep Talk on 3-5 pokemon in their team.