The sandbox tools might be useful in some situations, UncleP, but it did not indicate a problem with the domain we had trouble with. It showed the ads and gave it a green checkmark. I even tried the tools with a site that I know is heavily penalized due to the client's use of a crappy link builder. That site got numerous warnings in Webmaster Tools. It also passed.
Google did index the site and it picked up PageRank, so it was not banned. It was, however, prevented from ranking. We have been working with SEO since the 1990s and found no indication of any penalty, other than the fact that the site would not show up in the top 500 results for any keyword search.
None of those sandbox tools are actually Google tools. Even the one calling themselves Google Adsense Sandbox that infringes on their trademark is not owned by Google.
Other than using the Wayback Machine to see if a spammy site used the domain in the past, I have not yet found a way to verify penalties. Google is obviously not resetting penalties when the domain is dropped. The site mentioned in the article I cited was hit with just about every egregious penalty except poor quality link building. The only indicator that the author mentioned is a rejection by AdWords, which is similar to the way the sandbox tools are supposed to work.
Me thinks the trick to avoiding tainted domains is to avoid registering keyword-rich domains, which were highly favored by spammers.
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -- Benjamin Franklin