Here's what a quick search in google for 'caffeine hair growth' turned up:
"Eliminate or cut back on smoking, caffeine and carbonated sodas which weaken the body and block maximum hair growing potential."
"Study claims caffeine slows baldness
1/18/2005 - A caffeine extract has proved to be an effective ingredient in a topical hair loss prevention shampoo treatment, research suggests. Believed to be the only remedy to use this ingredient, the makers claim that huge concentrations can help prevent testosterone from damaging hair growth."
From:
http://davidhayden.com/blog/dave/archive/2005/08/21/2436.aspx
"Besides drinking green tea, lately I have been reading about other alleged benefits of green tea, such as green tea cream for skin care to fight acne and to help treat hair loss and promote hair regrowth.
Androgenetic Alopecia (aka Male Pattern Baldness)
Although both men and women can suffer significant hair loss, over 50% of men will suffer with Male Pattern Baldness (MPB), also known as androgenetic alopecia, at some point in their lives. The reason behind hair loss is a genetically inherited sensitivity to Dihydrotestosterone (DHT) and 5-alpha-reductase. The enzyme 5-alpha-reductase converts testosterone, a male hormone, to DHT, the substance identified as the end-cause for hair loss.
Green Tea Catechins
A study shows that the green tea catechins, epigallocatechin-3-gallate and epicatechin-3-gallate are potent inhibitors of Type 1 5-alpha-reductase (the enzyme that binds with testosterone to form DHT)."
And lastly,
"There are a number of foods and substances to avoid and limit the intake of. Substances such as alcohol, caffeine, sugar and nicotine
can deplete the body of nutrients and raise adrenal levels, which will cause a chain reaction of producing more androgen and causing hair loss. [notice it says 'can' not that they 'will' cause it.] High levels of saturated fat and cholesterol rich foods are also linked to increased DHT levels and their consumption should be limited. Additionally, common table salt has been linked to hair loss. And the average diet provides the recommended amount of sodium intake; therefore, salt should never be added to food. However, when using salt for seasoning during cooking, be sure to use salt with Iodine being that it is a nutrient that is vital to hair growth as well, unless you are a regular consumer of seafood, which contains high levels of Iodine.
Toxemia can cause a great deal of dysfunction in the body’s systems, including hair-loss related illnesses such as eczema, psoriasis, seborrhea and possibly several others. It is vital for one to cleanse the body of impurities in order to maintain a healthy system and avoid such illnesses, as there are no cure for these illnesses beyond cleansing and the maintenance of a healthy diet to allow the body to heal itself. Regular cleansing should include a diet rich in fiber as mentioned earlier, and the use of added fiber such as provided by consuming psyllium husk as a bulking agent along with laxative agents. More is discussed under the section Natural Hair Loss Remedies.
Although hair loss can be caused by many other variables, lack of proper nutrition will assuredly cause hair loss in many people. Fortunately, adopting a proper diet that includes the above nutrients can reverse hair loss caused by malnutrition. One thing for certain, regardless of whether your hair loss was caused by malnutrition or not, adopting a healthier diet will help the function of other areas of the body."
It is clear to me that there are arguments for and against it. I think I agree with the last bit that I posted about overall nutrition, it really doesn't have to do with caffeine itself. If your body doesn't have the right nutrition or isn't functioning properly then those substances have the potential to cause trouble for you.