An issue in software crowdsourcing is the quality of the task documentation and the high number of registered crowd workers to solve tasks but few submitted solutions only. This happens because uncommunicated or misunderstood requirements can lead crowd workers to deliver a solution that does not meet the customers' requirements or, worse, to give up submitting a solution. In this paper, we present an empirical study in which we analyzed task documentation and online forums messages associated with 25 Software Crowdsourcing (SW CS) challenges. The findings corroborate that weak documentation is a challenge in SW CS. Meanwhile, online forums allow crowd workers to gather additional technical and operational information that is not present in the official task documentation. We provide a stepping stone towards understanding the interplay between requirements and communication, to make it possible to improve SW CS development processes, practices, and tools.