We examine patterns of participation by employees who are members of multiple online communities in an enterprise communities service. Our analysis focuses on statistical patterns of contributing vs. "lurking". The majority of contributors (in one or more communities) were also lurkers (in one or more other communities). These results argue against hypotheses derived from common theories of participation and lurking. We propose that contributing and lurking are partially dependent on a trait (a person's overall engagement), modified by the individual's disposition toward a particular topic, work task or social group. Contributions include critique of theory, an analytic framework, and implications for design of community services. © 2012 ACM.