"https://nodejs.org/api/fs.html#fs_fs_readfile_file_options_callback" states that

Note: Specified file descriptors will not be closed automatically.

This is confusing for new users, because it implies that opened file should always be manually closed, leading to questions like this - http://stackoverflow.com/questions/21523890/close-file-after-fs-readfile-nulling

It should be mentioned that if "file" is specified as a filename, it will, indeed, be closed automatically.