I hand write the address clearly with black marker on the parcel and I take it to my local post office where they weigh and measure it and put the appropriate label on the parcel to show that it has been paid for.  Not sure if I am doing it different to other sellers.  I've never got into printing postage labels via ebay, etc.

I had the parcel sealed with masking tape and I think the girl at the post office may have put the label ontop of the masking tape rather than the actual cardboard box....so maybe it doesn't stick to masking tape as well?  I will be sure to avoid that situation again.

It stayed on from my Wollongong suburb as far as to Sydney where the tracking showed that it was in transit to Tasmania so must have come off somewhere along that route.

Yes, they were extremely irate which I can understand...but it was the outright rudeness that got to me.  There is a way to deal with things appropriately and not call someone a liar and a cheat.  I could even cop that on the chin with the initial message, as I would have been shocked by that situation if it had happened to me, but when it is explained to you and proof shown and then you get 3 more messages again calling you a liar and a cheat and several other offensive things.....that is uncalled for in my book