Not sure about where you are but when we did have stickers they didnt give them to you until you paid so I have no idea how you would get one without paying.   and yes some people swapped plates and stickers from car to car and probably still do.

NSW - we have just had the stickers discontinued from Jan 2013.  

Prior to that date the car rego bill sent in the mail had the sticker on it. So you pay your bill (online or wherever) and then you put the sticker on the car.

It was noted on the form you must not put your sticker on your car until you have paid your rego and recorded the receipt number on the form... form should be kept in the car from then on till expiry date.