There's a handful of things that have cropped over the years that I always thought everyone was edgy about, but it turns out the Australians I've been around haven't been remotely phased by. For instance:
--mail. If it's not yours, you can't possibly open it. Mail is like legal documents -- it's illegal to go messing with it if it isn't yours. (Hence, I refuse to throw out junk mail addressed to my flatmate.)
--going into grocery stores with items previously purchased from the same establishment. Freaks Americans out -- they'll think we stole it and we'll get in trouble if we can't find the receipt wadded up in the bottom of our bags. Hence, one also always keeps one's receipts wadded up in the bottoms of our bags. You never know, you know.