I'm no lawyer but I would be comfortable scraping a site if I had a letter from the site owner giving me permission to scrape it. As long as that website has original data! I guess if that site was illegally obtaining their data, and I knew that, then permission wouldn't be enough to keep me out of trouble. It's definitely a sticky issue.
As for the guy's website breaking every time the sites being scraped get updated-- let's just clarify what would actually break, and that is the scrape-and-update process. The website itself will be fine, it's just the data won't be updated until the scraper is fixed. Important distinction.