Vaporizers can't be used with tobacco. hehehe
It's really funny to me that people think that vaporizing somehow prevents cancer... Cancer is generally caused by particulates entering the lungs. The fact that the chemicals are carcinogenic speeds up the process, but even wood smoke causes cancer. Radon gas causes cancer... Non-Burned wood DUST causes cancer... Asbestos DUST causes cancer... Leather dust causes cancer...
If you think you are safe while breathing any sort of particulate matter into your lungs, you are deluding yourself. THC vapors are, I'm sure, quite harmful. Maybe not AS harmful as smoke, but in the long run, cancer is cancer. Also, most vaporizers achieve a RATIO of say... 80% THC and 20% Tar... It's simply better than an unfiltered joint... but not 100% tar free.