It seems pretty related in this case, since the kind of security that is being discussed here is around access to private data (and I'd note that it was you that used the word security here, not the OP who made the more correct contrast between openness and powerfulness).

One could equally make the point that Facebook is secure because no one has hacked their servers, and that it is open because it is free to join. That's a pointless thing to say though.

But in any case: yes, there is an inherent tension between privacy and openness.