Theymos assigns it on a whim to his friends people he considers experts.
FTFY
Also, I believe they only show up in a few sub-forums.
Can be both at the same time
I think it adds unneeded distinction. "Experts" have being wrong before (including Gavin on trivial things, for example thinking the difficulty cannot go down), and I'd hate for opinions or things to be folded away because someone is not an "expert".