My comment about orally ingesting it was aimed at the THC pill that doctors administer, not at throwing a bunch of it into a batch of brownies and munching away. The TCH pill is not as "powerful" so to speak as smoking a joint.
I personally don't advocate it's recreational use, but I do accept and approve of it's medical benefits. It is much cheaper, safer, pleasant, and more effective than many "legal" alternatives.
Many of my "facts" or arguments are from a couple drug and human body interaction classes that I took in college. All of my "facts" were in the text books and therefore I am unable to link any direct quotes/statistics to my information.
And as far as your friends who smoke that many joints, the tar may eventually catch up to them, and then again it may not. Peoples' bodies have different reactions to things such as that. Some people can smoke for 70 years and die of natural causes. But, on the other hand, there are thousands that die prematurely of smoking related difficulties such as cancer, emphazema, and heart attacks.
In everything, there are exceptions to the rule.