Viral marketing has become an increasingly popular promotional tool (Kirsner 2005; Walker 2004). According to a 2009 study by the media research firm PQ Media, spending on word-of-mouth (WOM) marketing rose at a compound annual growth rate of 53.7% from 2001 to 2008—from US$76 million to US$1,543 million—and is forecast to reach over US$3 billion annually by 2013 (PQ Media 2009). However, in a 2007 survey of marketing and advertising professionals by Dynamic Logic, half the respondents rated viral marketing as more of a fad than a mainstream and widely available tactic (Dynamic Logic 2007). One of the challenges faced by the viral marketing industry is the lack of formal quantitative and qualitative comparisons of this new promotional tool to traditional tools, and the scarcity of systematic methods for optimizing viral marketing campaigns. If, as recent forecasts imply, viral and WOM marketing become an increasingly common part of the marketing mix, then these kinds of challenges need to be addressed. This paper attempts to offer one small step in that direction.