Brenda,
I am glad you also brought up Open Space... a very powerful approach for encouraging emergent learning. I have a friend (Chris Corrigan) who travels the world facilitating open space workshops. These workshops happen everywhere you can imagine. Chris speaks often of holding the space to allow amazing things to emerge and to have the conversations that matter. Open spaces can be designed to encourage a trajectory, this begins with the invite (call for participants)... the invite is what would provide the rudder to the sailing ship, where the participants provide the wind.
I see this applies directly to online learning; where the facilitator, or group of peers, creates the invite. The invite sets the terms of reference (subject domain) of the learning and then those with an interest show up to the space. It is this pre-selection toward an interest that keeps in on track... but, amazing learning can emerge from an amazing number of directions, leading to new directions. But again, it is the invite (almost a social contract) that can bring it back into alignment if it strays...
$0.02
Peter