The standard Wiki in Moodle 2 doesn't allow groups to edit their own wikis but not those of other groups, and doesn't seem to understand groups and groupings.
I've posted re this issue here:
To summarize: In the standard wiki module in 1.9 it was possible to create a wiki in which, "There is one wiki per group. Students can change the wiki of their own group only. They can view the wikis for all groups." This was done with the following two settings
Group mode: visible
I do hope I am wrong about this and that I am missing something obvious, but none of the combinations of settings that I have tried allow for this collaborative group creation of Wikis.
The most obvious equivalent of this 1.9 setting in version 2 is:
Wiki mode: Collaborative wiki
Group mode: Visible groups
But this results in students being able to edit any group's wiki, not just their group's wiki.
I have selected the priority of this as a "Blocker" because it seems to me that Moodle is all about collaboration, and for such a fundamental ability to be lost (i.e. the ability for groups to create wikis without having them being edited by other groups) is a huge loss and for anyone trying to foster collaborative learning a Blocker of an issue. Until this is fixed, it is just not possible to do what was possible in 1.9.