My Panasonic plasma certainly doesn't do anything like that. When it is in standby it is dark.
This is consistent with the description in the Wikipedia article, saying that some plasma TVs show this issue and some do not.
I've never heard of anyone saying plasmas do that and I have a few friends with those Pioneers.
Possible explanations:
- It exists on your friends' Pioneer displays, but your friends have not noticed it because the issue is subtle.
- Your friends have newer models which don't exhibit the issue.