Imho, the amount of smoke depends on what you are cooking and how they are served. Butts can take alot, and I kind of prefer it that way so it's not masked by the sauce. The problem with a lot of so called BBQ joints around here at least is, once you put on the sauce, you loose the underlying smoked taste of the meat.
Obviously, with anything you can go overboard, but I think the trick is to find a balance on the amount of smoke with every meat so that whatever you serve it with compliments the final result. Smoke is kind of the percussion or bass to the sauces guitar. More delicate meats like chicken, turkey, and especially fish don't need much.
Pretty basic logic there, but I've had an awful lot of BBQ out there that don't seem to get this.