I'm helping to edit a book for O'Reilly, and we're keeping details on contributors, and the status of their chapters, in a little SQLite database. The database file is kept under version control, since everything should be; unfortunately, Subversion doesn't know how to diff or merge concurrent changes. I've griped about this before: just as languages become more useful when functions and classes are first-class values, so too do data formats become more usable when they are supported by tools that let people create them collaboratively. Moving the data itself onto the web (as I suggested to scientists who are using Excel spreadsheets as structured lab notebooks) is a stopgap measure: the real world will always require people to work offline from time to time, and we damn well ought to support it.