The back and forth has been very interesting, and seemingly inconclusive, though my general impression is that a 1-1 mapping between classes and files is the majority opinion, though with some person-by-person exceptions.
I'm curious if any of your answers vary depending on whether you are: (1) developing a Windows Forms app, a Web app, a Library, or whatever; or (2) using Visual Studio or not. In using VS, it would appear that the one class per file rule would also imply one class per VS project since the concensus in other threads seems to be that VS solutions/projects should be mirrored in the directory/file naming and structure. Indeed, my impression is that the concensus is to have the project name = assembly name = (nested) namespace name, all of which would then be mirrored in the directory/file naming and structure. If those are the right guidelines (or rules), then all these seemingly orthogonal organizing mechanisms would be nevertheless kept in sync.
