Getting an ABN is not a difficult thing to do and if you look further into it all people carrying out any type of business in Australia are required to have one, whether they are a registered business or not.
We will add a new field to the Supplier directory so suppliers can indicate whether they require resellers who deal with them have ABN or not.
Businesses outside Australia do not require are reseller to have an ABN, although this would be a good check for the legitimacy of their resellers.
ABNs can be checked at at business.gov.au
There is also more information about registering for an ABN here
In our opinion it is not wise to trade without an ABN and it has advantages (like claiming GST back on purchases).
Hope this is helpful.