Today’s social computing platforms include many open content fora where users voluntarily create and edit content online. This has opened up a new mechanism for knowledge acquisition raising related research questions, including identification of the reasons why people contribute to open fora. While altruism is mentioned most frequently, it has been suggested that there may be additional drivers in play. To explore this possibility, we examine contribution behavior in the Wikipedia context using qualitative data from two focus groups of Wikipedians. Content analysis of the data reveals a number of different drivers of contributor behavior which we then map into the Motivation-Ability-Opportunity (MAO) theoretical framework developed in the organizational behavior literature on work performance. The mapping can provide a theoretical basis for quantitative examination of contributor behavior and lead to more effective methods of managing collective knowledge in other open forum settings, such as corporate wikis.