Gotta admit there are a number of things I look for before dealing with anyone, ABN, physical address and phone number, email address.
Of course there are more and more online only stores cropping up, but it's also a factor of what your actually buying. Lots of small stuff I will just order and hope for the best, larger stuff you can usually get your local DSE to price match (that and you get local warranty/returns as well as that instant gratification you don't get with online purchases :P)
But bottom line, I'm with you, online businesses should at least cover the basics on their websites.