Joy Fairbanks provides an article that offers guidance for founders and investors evaluating market opportunities. There are three tiers of scale commonly used to calculate the market opportunity for a startup’s product or service offering:  TAM, SAM, and SOM.  These are acronyms for Total Addressable Market, Serviceable Available Market, and Serviceable Obtainable Market.  The purpose of these market assessments is to determine not what is, but what could be.  Founders, you may be struggling with calculating and interpreting these…