In this paper we aim at discussing cognitive and epistemic features of online communities, by the use of cognitive niche constructions theories, presenting them as virtual cognitive niches. Virtual cognitive niches can be considered as digitally-encoded collaborative distributions of diverse types of information into an environment performed by agents to aid thinking and reasoning about some target domain. Discussing this definition, we will also consider how online communities, as networks displaying a social bias, can both foster civic awareness and promote (...) problematic group-led behaviors in the virtually aggregated crowds. To support this affirmation, we will take into account the use of online communication networks during crises and we will argue that it can lead to ethically dubious consequences. (shrink)