An apparatus, program product, and method analyze electronic messages directed between individuals to quantitatively assess the relative communication capabilities of such individuals. A quantitative value referred to as "communication strength" is determined for one or more individuals from a plurality of individuals based upon analysis of the electronic messaging activities of such individual(s), and is subsequently used to select an individual from among the plurality of individuals, e.g., for the purpose of selecting a target for a viral marketing encounter, a market research project, etc. The communication strength of an individual is determined by modeling a plurality of conversations identified through analysis of a plurality of electronic messages generated by the plurality of individuals, where each conversation is associated with a talker and a listener from the plurality of individuals, and is useful in determining a level of messaging activity between the talker and listener associated with such conversation.