Earlier quoted context omitted.
"probably" doesn't lead to "yes, it works". What's the tradeoff? How many good actors does "probably" imply?
Ok, say you are tracked by google, facebook, adzerk, and twitter. If you set DNT, you are now only tracked by google, facebook, and twitter. Yeah, it was pretty much pointless, but you are being tracked by one less network, so it worked to some extent. It is trash, but at least it is something.
Compelling arguments in favor.