RF Chokes/Ferrite Beads, do they have a place in your system?

Thanks all, I appreciate the description of how a ferrite choke works.

I have noticed that certain electronics in my home such as some HDMI cables, computer system cables, and power cables came from the manufacturers with chokes molded right into the cable or clamped on such as my Audioquest power cable. What is it that these manufacturers are trying to accomplish by installing the ferrite chokes on all of these different types of cables? Are they trying to reduce radiated noise or are they trying to stop something from entering the equipment from the AC mains or something in the signal chain? Thanks! 

Mofimadness, please comment on the effectiveness of ferrite clamps
over power cords.  The largest I have been able to buy is
13mm.  Do have have much larger ones, perhaps for sale?

@sgordon...I find RF Chokes work quite well on AC Power Cords, just don’t over do it.

Sorry, I sold most of what I had. Not sure how large they were, but they worked on pretty big cords.

IIRC, I bought all of mine from Digikey.

You can destroy the transfer rate of a digital cable with the benign placement of a ferrite to lower RF. Maybe on the output cable of a switching power supply. However most manufacturers already have them. Bottom line it's a lot easier to do harm than good. RF is a real problem. The FCC is supposed to test all electronics for excessive RF, but that is little comfort to audiophiles who own sensitive gear. Think of the RF inside a desktop PC.(At least laptops run on batteries.) This is why a whole new component has emerged: AC filtering devices. They all have their pros and cons. There is many different technologies with every designer saying theirs is best. There is a good paper on Audioquest's site with the engineer eventually pushing his own.(I have a discontinued PS Audio Duet.) But don't put a ferrite or choke on your USB, coaxial, HDMI, etc. Toslink isn't a problem, but they have their own issues. Audioquest's Jitterbug and iFi's Silencer 3+ are good products for USB.