Ooooh, I never knew this Backing Up MarsEdit:
MarsEdit stores all its data in a folder in your home folder. To open the MarsEdit data folder, hold the option key on your keyboard while selecting the Help menu at the top of the screen, then select “Open MarsEdit Data Folder.”
Dave Winer -- i'm not familiar with the UI, but it seems this is a very important function, why make it so inaccessible? don't the users need to know where their data is?
Miraz Jordan @dave Well, I'm not the right person to ask about that — better to ask the developer. For those who work heavily with local drafts I guess there could be a need, but for me MarsEdit handles posts that are already published on a server so while I'm interested to know where MarsEdit stores its data it doesn't feel crucial.