I have seen on this and many other forums, people asking if they will get dvd's etc confiscated when they get back into australia.
My brother is a customs officer and he has explained it to me that the only way anything will get confiscated is if its very obvious they are to be onsold - ie 100 copies of "gladiator" - or 100 hats/watches etc. Really, bringing in multiple items of anything that are the same will raise a flag.
If you buy 100, 200 or 300 dvds they wont care as long as most of them are different.
Same with alcohol they say you can only bring in 1 litre. But you can bring in more than that if the bottles have been opened and have something out of them. I wouldnt go crazy here and try bringing in 5 bottles or anything, but if you have a part bottle that you didnt drink from your duty free (god forbid!!) you can bring that back as well as purchasing a new bottle back at home - duty free. Last time we went, we brought in 2 bottles each (one opened and one unopened)
Hope this helps :)