1script - 2:33 am on Jun 8, 2010 (gmt 0)
I need to restate that for clarity: the "404-like content" error shows on the dynamic URL that initiates the 301 redirect, not the intended target of redirect. I assume the result is the same though: the link juice (for lack of a better term) is going to stop at the intermediary redirecting URL instead of flowing to the final destination URL.
I'm curious about the false positives. Are any of them NOT the target URL of a redirect? I would also hope Google's heuristic would need them to be the target of more than one redirect.
The regular "200 OK" page labeled "404-like content" in my other example is, obviously, the final (and only) URL.