Malicious Linux Instructions

Tom Dryer offers some good advice to novice Linux users concerning the execution of malicious terminal commands/shell scripts:

Don't run a command if you don't understand what it is doing and don't run commands from untrusted people or places. Check with someone you trust if you are not sure, or check out the command's manual page.

Tom's advice is sound, but I fear he's shouting into the wind. I read the same Ubuntu forum announcement as Tom and while I've always been aware of the issue, it's worrying to read about it on such a high-traffic site as Ubuntu Forums — more so considering the site is heavily used for system support/help requests.