Another post from Anouk who makes good points about collaboration.
Some key ideas:
"Dillenbourg writes: “A first way to increase the probability that some types of interaction occur is to carefully design the situation.” "Real-life problems that reflect systematic differences between learners, or complementarity between learners’ skills require rich interactions".
"The role of the e-facilitator is paramount in the success of collaborative learning."
Anouk's blog is always worth a read imho.
http://dynamind-elearning.com/2014/10/are-you-designing-for-cooperation-or-collaboration/