tedster - 12:19 am on Oct 18, 2012 (gmt 0)
Again, I apologize that my remarks above were incorrect and based on partial information.
I think the main point here is don't try to be preemptive in using this tool, use it only if you already have ranking troubles. I've already heard of people who are disavowing any backlink from a URL with a PR below 3, even though their rankings are fine. That's really not a good idea.