[Amps] Plate choke magic?

[Tomm Aldridge]

Why are plate chokes seemingly black magic?  Don't you just want a good 
decoupling of the PS from the Plate; i.e. lots of impedance from DC to 
Light and no resonances?  How I get that should not be an issue but all 
teh plate chokes I see are long skinny and sometimes segmented single 
layer solenoids of questionable wire size.  Why wouldn't a really lossy 
powdered metal toroid with a few fat turns on it work, assuming the 
inductance was high enough?

KD7QAE