If you have large JSON files with application settings in, you need to be sure that the settings only appear once. Not a problem until you get to the stage of very large files, being edited by all sorts of people manually.
[ "setting_1" : "some value", "setting_2" : "another value", "setting_1" : "different again" ]
Run a script to check for duplicate key names:
grep -Po '"[a-z_0-9]+"[ ]*:' <filename> | uniq -d
The above will output the duplicated setting(s) if any, to the console. Tested on Ubuntu 12.04