Internet Archive Never Forgets
theringer.com
theringer.com
If the archive had more common sense, they'd note down when sites and robots.txt files change and only block pages by the site owner with the offending robots.txt file. So if say, Google went under and a new company started up, a robots.txt file from the latter would only block files added since the site switched over.
That would solve 99.99% of these issues.