I can't think of any examples mixing journals with non-journals, but some of the considerations are written up here in the FAQ
. Perhaps the major consideration is whether you'll need to modify the application to handle non-journal content, and if so, what the ramifications will be considering that you'll be hosting both types from the same codebase. (Modifications that take this into consideration are possible, but will probably involve a lot of conditional statements to manage both types.) Note also that while it's fairly easy to split a single installation into multiples, it's very difficult to join separate installations back together again into one while preserving content.
Public Knowledge Project Team