Potential engagement issues
Whilst this is true, it should be pointed out that there have been well-documented engagement issues associated with open source scientific endeavours such as science wikis (see Nielsen’s Reinventing Discovery, Ch.8). It has for instance been difficult to mobilise the academic community, whose activity is largely focused on publication of articles in peer-reviewed journals.
And indeed, those crowdsourcing projects that have mobilised academics, such as Polymath, have largely been conducive to improving their publication record. It strikes me that this issue is a potentially serious one.