When I started smoking weed, I was taught to mix the weed w/tobacco and roll a joint/spliff. After I stopped smoking cigarettes I fell out of smoking weed for a while until I discovered bongs.
I felt that mixing tobacco and weed can definitely increase the addiction potential of the former.
Never mixed weed/tobacco in a bong - that would screw up the taste of all my glass and probably start me on cigarettes again.
Tom