Widespread participation in collaborative writing and public discourse on blogs, news sites, Wikipedia and other online information sources is creating a new class of information literacy skills. In a series of qualitative studies, I examined high school students' information assessment practices as they helped build a collaborative online information source. I identified two types of strategies for assessing information sources: first-order strategies involve adopting known heuristics for assessing sources whereas second-order strategies involve reflective construction of standards based on students' understanding of how information is produced and the tasks in which they are engaged. I link these constructs to the literature on knowledge building and use them to explain both information assessment strategies and how participation in information production on open collaboration platforms can provide learners with a concrete vantage point from which to consider the information sources they use. Moreover, I find that learners can experience responsibility for contributing to new knowledge in several dimensions, including a shared and individual sense of responsibility in both local and global contexts. Finally, I discuss implications of these findings for research on collaboration and learning as well as for educational practice.