Peter, thanks, you articulate it so well:
I believe the plan and design can create the trajectory of the learning, just as MOOCs have created the trajectory for many emerging pedagogies, etc... and it is the MOOC that brings things back to alignment with the trajectory. Emergent learning often strays, it is the plan and design that brings it back..
We came across a lovely metaphor in Rose Luckin's work, on 'lines of desire' ...
which seems to capture some of the interaction between design, alignment and emergent trajectories. See more here ...
Next paradox ... arising from what you write ... Agreed, "a number of people are not social", but ... they too use social media, like this, to forage for nuggets that they can take away and 'think on' and 'think with', no? I do.
I am not a great fan of the term 'heutagogy' (although I support the concept, like you do) but I must admit that I do like playing with the mashed up term 'heutaculture', which is the best (obscure, unfortunately) term I have for designing for emergence.