I just came across this little incident on another forum and since this old thread was revived recently I thought some of you might find it interesting.
The fella that was telling what happened said his uncle had a small compressor that was about 20 years old and they had forgotten to unplug it and the tank let go on the thing during the night. He described the tank as "opening up like a banana peel" and going through the metal siding of their small garage where it left a hole big enough for a man to crawl through. They found the tank about fifty feet away from the building and the pump about 100 feet away, he said they could not even find the motor! He ended the story by saying he has become a big fan of hydo testing after seeing that!
While tank ruptures are not exactly an everyday occurrence they do happen and sometimes it can get real serious. Injuries and even fatalities are sometimes the result of these failures and property damage besides the compressor itself is likely in the event of a failure so it is a very good idea to treat these things with respect and DON'T TAKE CHANCES!