Communication among medical informatics communities can suffer from fragmentation across multiple forums, disciplines, and subdisciplines; variation among journals, vocabularies and ontologies; cost and distance. Online communities help overcome these obstacles, but may become onerous when listservs are flooded with cross-postings. Rich and relevant content may be ignored. The American Medical Informatics Association successfully addressed these problems when it created a virtual meeting place by merging the membership of four working groups into a single listserv known as the "Implementation and Optimization Forum." A communication explosion ensued, with thousands of interchanges, hundreds of topics, commentaries from "notables," neophytes, and students--many from different disciplines, countries, traditions. We discuss the listserv's creation, illustrate its benefits, and examine its lessons for others. We use examples from the lively, creative, deep, and occasionally conflicting discussions of user experiences--interchanges about medication reconciliation, open source strategies, nursing, ethics, system integration, and patient photos in the EMR--all enhancing knowledge, collegiality, and collaboration.