I'm already doing it!
I have participated in the thread zombiehair is talking about, and I have been putting semen on my scalp for about two weeks by now. Apparently, spermidine is a hair growth promoter, and also, semen contains a lot of PGE2. But it has to be "natural" spermidine, that is, the one which comes from your own semen, as synthesized spermidine lacks the key prostaglandines (or so I heard). I am applying semen in areas where I don't have hair loss, as apparently, too much spermidine can be toxic to hair follicles, so we first have to find the limit our follicles can take. I have been putting semen in areas of my scalp two times a day for two weeks now. Some would say that may be overkill, but up to this point, my hair seems fine, it has not be damaged. But, as I am applying the semen on areas of my scalp where I don't have hair loss and have a very thick hair I can't say I am seeying anything positive (I suppose I wont be seeing any change there, as my hair there just can't get any better or healthier, but the first thing I want to find out is if too much can damage my scalp or not, and how much is too much).
My only doubt is to know if semen is a good vehicle by itself or not. And also, I'm still waiting for my dermaroller to arrive.