> This of course completely false - which is why we use filesytems and files, more than we use databases ;-) But consider: there is no application in existence

> This of course completely false - which is why we use filesytems and files, more than we use databases ;-) But consider: there is no application in existence that attempts to work with the contents of every kind of file that can possibly exist on a filesystem. The only kinds of information that any application can reasonably aggregate across all files are those which conform to the standard metadata schema the filesystem applies to all files. Creating an application that aggregated anything else across all files is essentially impossible -- no sane human would attempt to write an application whose functionality depended on them writing parsers for every single file format that could possibly be found in a filesystem. And yet, for most uses of MongoDB it is acting as the datastore for a single application, which in order to do any number of things normally demanded of applications (queries, aggregations, CRUD, etc) must be able to read every variety of document that anyone has ever thrown into the datastore, whether those variations were planned (lets add the following fields to all new Comment documents) or accidental (whoops, a bug led to 3 days worth of Comments missing one or more of the following fields). In the latter scenario, the "it's like a filesystem, store whatever you want!" actively works against the controlling the complexity of the application, to the programmer's great detriment.