> I'm going to use robots.txt until Blekko changes its stance on this one.
Yep. That's the answer for now.
I will ask Rich to comment.
> What worries me more are major sites like the Wayback Machine
> archive.org ignoring the noarchive tag...
and archive.org offers you NO way of removing back content. Their system in place, simply doesn't work. The only way to remove it, is via a lawyer.