Rule 4.2 of the .com.au domain policy states that domain names are not transferable. This is in contrast to the regime applicable to off-line business names. As a domain name is analogous in most respects with an offline business name, I believe policies applicable to the two classes of name should be made as consistent as possible. 

Many offline businesses build up a large goodwill value under their business name. The owner can realise this asset because it is certain that the name can be transferred to a buyer.  Online businesses with goodwill in a domain name do not have the same certainty. The best they can do is undertake to a buyer to deregister the name on the sale going through, with the buyer then immediately applying to register. Of course there is a risk that someone else could beat the buyer to it, or the registrar may decide that the applicant is ineligible. Not a risk I'd take if I was paying any serious money for a business. The .net.au registry once allowed me to send an off line deregistration and re-registration in the name of the new owner at the same time and processed them simultaneously, but it may not be official policy. If a domain is owned by a company, the sale of the company rather than its business results in the effective transfer of the name without registrar involvement, but there can be problems with buying companies instead of their assets, and the due diligence threshold is much higher.

One objection to allowing transfers is that the buyer of the name may have a business name from which the domain name is not derived. If you accept for the sake of the discussion that the derivation rule is fair, there is another way to protect it in this case. 
A buyer and a seller could submit a transfer application for pre-approval before money had changed hands. If the registrar was satisfied that the domain was derived from the buyer's business name, it could issue authorisation for the transfer to proceed, open for say 1 month. As long as an actual transfer was submitted in that time which complied with the pre-authorisation, the transfer would be registered. The buyer and the seller could have as a term of the sale that the sale was off if the pre-authorisation was not granted.

Stephen Gethin
IT Lawyer

This email represents my own views and not those of my firm. Where this email contains comment on legal issues it should not be considered legal advice. (I know that you don't think that it does, but I have to say it anyway.)