I am also very interested in walking as a participatory tool and excited by an opportunity to focus on this. I think Emily is asking some really good questions such as, Why do walking practises create such good spaces for exchange? I would add, what is the impact of the environment on the converstaions we have?
I worked with artist Anthony Schrag on a walk with visually impaired participants that is documented on the project blog: http://artlinkambition.wordpress.com/2012/03/13/along-the-ledge/
I found documenting this quite challenging so it would be good to think about this some more.
I am planning another walk with Anthony and he is Tourist in Residence at Edinburgh Art Festival: http://www.edinburghartfestival.com/commissions/anthony_schrag/
Liz Lerman is another interesting artist and I think her Treadmill Tapes are a good example of documentation. she is based in america but will be in edinburgh in november: http://lizlerman.com/tredLL.html