Here's what appears to be a legitimate study with biotin that was published in a European medical journal. I'd certainly like to see other corroborative evidence for their findings, but maybe there's some truth to it:
Authors: Floersheim GL.
Institution: Dermatologie FMH, Rennweg 15,CH-4052 Basel; Switzerland.
Title: "An examination of the effect of biotin on alopecia and hair quality"
Source: Zeitschrift fur Hautkrankheiten. Vol 67(3) (pp 246-252+255), 1992.
Abstract: "The effect of a daily oral dose of 2.5 mg biotin was studied in 93 patients with the symptoms hair-loss (mostly androgenetic alopecia) and reduced hair quality. The mean duration of treatment was 7.9 +/- 2.8 months. An obvious improvement of hair-loss was reported in 64%, and a slight improvement in 9%. Hair quality was clearly improved in 70% and slightly in 12%. Brittle finger nails as an additional complaint were improved in 80%. If alopecia, decreased hair quality and brittle finger nails occurred in combination, improvement was observed frequently collectively. The study allows - as already shown in a previous investigation concerning brittle finger nails - to suggest biotin as an effective and well tolerated therapy in cases of alopecia and decreased hair quality."
Bryan