I disagree ;) . It can be invaluable to include an inductor in the ground path in order to 'decouple' two 'grounds' and prevent nasty ground loops. As an example, a mains powered industrial indicator will have a 'safety earth' connection (required by law), but may have alternative earth connections via sensors, or even the physical enclosure. If the safety earth is 'noisy' you have classic ground loop problems. Take a look at the best quality (dual filter) Schaffner mains filters as an example. They also have a earth series inductor.
Dave