I thought that at first myself but after a bit more examination I found that the far right button in the mouse over menu bar has an option for share. That is for the Pro account though, I don't know if the mini has it.
I looked at the price plans, now realizing you may have already done that, and though it has been updated since I looked last, it now has a Viral Tools section, it does not mention the share feature. It has the mini with the Invite feature limited to NC's only and none of the others. At this point I think we need someone from Ning for clarity cuz I am out of ideas.
EDIT: For anyone who cares the link to the plans is...