Since this was the only good discussion on this topic I feel obligated to respond. Most ground was already covered so I'll attempt to be brief.

Sub-lingual and injected THC will NOT work since it is fat soluble and not water soluble.

And from every article I have read on the subject, there is no link between smoking marijuana and cancer or other lung diseases (although this doesn't mean there isn't one, just that it's not an obvious one). Contrast this with cigarettes where the link has been proven time and time again to the point where we calculate the amount of deaths per yer due specifically to the drug. Although since it came up, this doesn't mean I am for making tobacco illegal.