Magnetic shielding works on the principles of the faraday cage, except in reverse in the above example. If you have a strong conductor surrounding your dipole, any transients created by the dipole are equalized inside the conductor instead of your cathode ray tube. Magnetic shielding is also a good thing to have on your monitor if you're worried about getting TEMPESTed by someone unsavory. When Bill Clinton gave his closed-circuit grand jury deposition in the Lewinsky case, the TV set he appeared on was shielded for just this reason.

Most of the time, however, designers put magnetic shielding on a piece of equipment because they're worried about outside magnetic currents effecting their own gadget. Computers are a good example of this, and entire labs can be magnetically shielded if they are doing any sort of research with radiofrequency applications.