In this paper, we present findings on moderation of synchronous, small-group argumentation in blended, co-located learning environments. Drawing on findings from the literature on human facilitation of dialogue in face-to-face settings, we first elaborate on the potential promise of this new practice. However, little is known about what constitutes effective human facilitation in synchronous e-discussions. A multi-method exploratory approach was then adopted to provide first insights into some of the difficulties and characteristics of moderation in these settings. To this end, we focused on (1) students' perspectives on what constitutes effective e-moderation of synchronous peer argumentation in classrooms and (2) the relations between characteristics of actual and perceived moderation effectiveness. The analyses presented in this paper reveal that the role of the e-moderator in synchronous peer discussions is a complex one and that expectations from e-moderators seem at times even contradictory. Also, comparisons with findings on moderation in other communication formats (e.g., asynchronous, face-to-face) show that insights on effective instructional practices in these formats cannot be simply transferred to synchronous communication formats. We close this paper by briefly describing a tool that provides real-time support for e-moderators of synchronous group discussions, and whose development had been sparked by these findings in a further cycle of our design research program. Several questions and hypotheses are articulated to be investigated in future research, both with these new tools and in general.