As suspected, the Vegemite-banned-in-the-US story turns out to be bullshit.

"The US government has dismissed media reports it had banned Vegemite......"There is no ban on Vegemite," US Food and Drug Administration (FDA) spokesman Mike Herndon said."

Terrorists, take note. If you want to smuggle some dangerous poison onto a plane, conceal it in a salty black paste, and put it in a Vegemite jar. Or just use the Vegemite as a poison - most non-Aussies are such big girl's blouses that they can't handle the stuff anyhow.