Really interesting post about encouraging reflection.
Just getting people to start contributing online can be a challenge, let alone starting thinking “in what way…?”, and especially if they are mature students.
I found a closed facebook group which could feed into extra participation and peer assessment marks worked well with adult learners. It encouraged people to contribute ideas and comment on resources their peers introduced but using a forum most were already familiar with.
However, it is hard to avoid excluding people unless you provide a variety of ways they can gain the marks – this Forrester survey http://venturebeat.com/2010/11/11/forrester-privacy-concerns-faceboo/ indicates about a third of people are really concerned about their privacy in using facebook. About a tenth of my students did not want to interact using facebook if they could avoid it despite it being fairly key to their subject (digital marketing).