I found a webmaster job site that allowed a post to be made in which the author asked the contractor to go out and copy reviews for 3 sites (one of them being mine) in an attempt to start his own site with the plagiarised reviews on it.
The job was completed and the post is now closed. Apart from the author's username, I have no other details.
The job site is fairly well known, supposedly "connecting thousands of professionals".
What can I do to have the site reveal the author's site/identity so that I can take action under DMCA?
The author has an "excellent" rating on the site for paying people to do his dirty work. What steps can I take to have the job site ban his account, to prevent future postings of this sort?