I would not go as far as saying POT is completely harmless.  Just see what happens when you are lying in bed, toking to the extreme and you pass out.  A hot Roach sharing the bed with you can be extremely painful, if not fatal...  I found  this blog page for the comparison between mortality rates of seemly  harmless activities and "friendly" animals and ends with the fact that POT has never been blamed entirely in the death of any living creature in over 5,000 years of use.  It really puts things in perspective.  Enjoy!