I hate any kind of buzz. But, I love my three month old Pioneer KRP-600M (N.American) which has more much more buzz than my six and a half year-old Panasonic 42" ED.
I discovered a way to induce a loud, annoying buzz. Fortunately, I did not discover this until weeks after I convinced myself that "my Kuro" had zero buzz issues. I know it is a very infrequent occurance for me.
First, I go to a website such as Bloomberg.com with an all black background ( I use the white bkgrd option for AVSforum). Then I zoom in and scroll around until the upper-left corner of one of the super-white boxes is positioned to cover exactly the lower half and middle-right two-thirds of the screen. The suddenly very obvious buzz reaches a peak so loud that it cannot be ignored by two people conversing twelve feet away. Fortunately, the buzz drops off significantly by almost any relocation of that white box. But it is still there in a slightly annoying form.
The good news is that, now that I know what causes it, it does not irritate me that much. I can avoid it altogether on the very rare occasions that it crops up. I have never heard the buzz with a movie playing and once or twice when I was watching TV. I think that was a football game on ESPN with the standard box of stats. I have seen that same graphics hundreds of other times with no audible buzz.
A weirdly related discovery under those extreme conditions, is that putting my hand six inches on the perpendicular from that exact area of the white box, I can feel the screen emitting intense heat just like putting your hand within six inches of an IR heat lamp.
My conclusion is that the buzz is likely the result of the design. I do not think that is really so bad, as the remedies would include lower plasma voltages, smaller panels with heavier bracing, thick double pane glass and much heavier and thicker PDP construction - just like the old, much more expensive, lower fidelity Panasonic I have in another room.
Now, YMMV, because many other factors affect our ability to hear the buzz. I once lived so far from civiliztion that I found the buzz from 60 HZ incandescent light bulbs to be so annoying that I could not stand a table lamp less than two feet away. The same lamp in my very quiet house in the 'burbs of a major city emits 'zero' buzz.
On most bright program material, there definitely is a twice or three times as audible buzz than my old Panasonic if my ears are very close to the front (less than two feet) or within four feet of the back.
Thanks to reading this thread, before ordering, I expected much worse. I am really pleased that my panel has zero buzz - UNLESS I stand really close to it or display super-white in the lower right quadrant. Super-white displayed over the entire screen has much less buzz.
Finally, I am sixty years old. It is possible, some "dog-earred" kids might hear some super harmonics that I no longer can hear, but I think a lot of other high-pitched noise makers such as hard drives in DVRs or Blu-ray motors and servos might compete.