For me its the harm that could come if generally one went dosing random people around with a psychedelic, let alone a quite powerfull one such as DMT. By the way, such an approach has been tried in the past (mainly with other psychedelics) and the results were less than stellar: check out the 60's.Its also a hmmm...quite stereotyped stage in the "psychedelic growth" of a person,usually seen in people with lots of enthusiasm for having discovered this class of substances : they want to dose the world, its the "psychedelics in the watersupply" scenario :d .
You could expect some psychotic reactions,some panic attacks ,the whole assortment of such stuff.This is not only a fuction of "readiness" (which can dangerously sound like "worthyness" ) but also the sum of who is a person and what situation he/she is into: the human individuals come in many flavors,even in smaller choices you can see those subtle -or not so subtle- differences that make them better geared toward different life paths!Now, here some people that consider it "panacea" (hmmm be weary of "panaceas") ) or "instant enlightment" might oppose to what i say.Its what you consider it to be: if you consider enlightment or <insert your favorite term> an intrinsic quality of those substances no matter who is the person or what is he/she into, then yes it only takes contact with the substance to "see the truth", "be enlightened" ,<insert goal you believe you are achieving through it>. I dont consider it intrinsic though...I think it takes a wee bit more than someone smoking 50-60 mg of DMT.