My only major concern about hair multiplication is that cells from the scalp are expanded considerably in culture. To make cells proliferate in culture, you have to maintain them with serum and/or growth factors to prevent them from exiting the cell cycle like all skin cells are designed to do, eventually. This temporary period of hyperproliferation may lead to expansions of a certain sub-population of cells that has greater proliferative capacity. This greater proliferative capacity could be due to a mutation or mutations that affect cell growth. Under the right culture conditions, such cells grow like crazy, and can easily expand several-fold faster than their more normal counterparts. So now you've got cells primed for transformation (meaning they are more likely to become immortalized tumor cells) that you've expanded disproportionally in culture, and you want to put them back on your relatively hairless head, where they're exposed to sunlight, etc. Not a good idea, IMO, unless this procedure is stringently tested and shown to NOT lead to the unnatural expansion of incipient tumorigenic cells. If you're a burn victim, such a risk is reasonable. If you're just bald, I dunno.
