Byron Capital Markets is out with a good need dose of reality and humor on the Facebook Inc (NASDAQ:FB) IPO. The firm compares the valuation of Facebook to eight other tech giants and shows how absurd the numbers for Facebook are. They challenge readers to use any numbers in a model to justify the valuation. How Much Earnings Growth Is Needed? We blow the dust off a tool we developed about 12 years ago in the (last) tech bubble that helped us judge the level of valuation insanity. Basically we use a modified multi-stage DCF to calculate how much…