If you have an aluminum cylinder, it won't rust like that and become "ANOTHER BOMB!"
...and the guy who blew his arm off because he used the wrong "reducing valve" (read, "regulator") is a testament to the fact that working with high pressure gas is indeed dangerous...especially if you're an idiot.
I think I'll find my doom and gloom somewhere else. I get my gas from a licensed and reputable dealer with whom I have a great working relationship.