The context is PAFlow, which is a "pure" (no CMF/Plone) vertical application for (italian) public administration.
Inside this application, we are using an in house developed framework where more or less each page shown to the user is connected to an object (which we call controller) on the ZODB.
When one user requests a page, PAFlow creates a controller for it (actually, creates also the page, but this is not important now), storing there all the data meaningful for that page, so that later the page can be built simply by invoking methods from the controller (I hope this is clear, otherwise I will post some code example).
All of this sounds quite cool but smells complicated. I don't see a need for multiple temp_folders. Just stick folders (for each instance) and folders inside them (for each user). Good luck -- Peter Bengtsson, work www.fry-it.com home www.peterbe.com hobby www.issuetrackerproduct.com