Snoopy to some extent I agree with what you are saying, if you had a hyphenated domain you may loose a small amount of business to the same domain without a hyphen although in my opinion I tend to agree with DavidL that it would be a negligible amount.
From a purely domaining point of view of course the exact match domain without a hyphen or hyphens is best, there is no denying that. I think though the point is not everyone can own a category killer exact match domain without a hyphen and for many of us the next best thing is the only option because either the exact match non-hyphenated domain is not for sale regardless of price or if it is for sale it is not within budget. So the question then becomes what is better - a hyphenated domain or a domain with other words in it? What would loose less business?
Lets say John had a business selling electronic sensors, the domain electronicsensors.com.au was not available or the owner wanted too much for the domain or John just could not afford what was being asked for the domain. So John now has to choose between electronic-sensors.com.au and johnselectronicsensors.com.au or *someword*electronicsensors.com.au. In my opinion John would still be better off going with electronic-sensors.com.au. I think the small disadvantage of the hyphen is also present with an extra word in the domain without the hyphens. In other words johnselectronicsensors.com.au will also probably loose a small amount of business to electronicsensors.com.au in the case where people forget the domain name. The point I am trying to make is that unless you have electronicsensors.com.au you are at a slight disadvantage, hence the inherent value of exact match non-hyphenated domains, no matter whether you choose electronic-sensors.com.au or someotherdomain.com.au. I don't think adding an extra word is in any way a more logical solution.
There are more and more US businesses running websites on hyphenated domains and I do think they are becoming more accepted and it will only be a matter of time before they become more accepted here too.
Snoopy what bugs me about you argument is that you sort of give the impression that unless you have the non-hyphenated 'best' domain it is just not worth it and that you may as well just give up and find another business idea. Whilst you obviously know your stuff and have, from what I can gather, made alot more money from domaining than many if not most on this forum and respect where respect is due I do think your argument is not helpful for two reasons. One, many people do make good money on hyphenated domains as developers. If you can make $100,000 on some-domain.com.au that is $97,000 more than nothing even if you do loose 3% of sales (which I think is much more than you would actually loose). Two, I think it is in all of our interests to lift the .au domain industry as a whole. Telling everyone that their domains are worthless 'crap' unless they are category killer non-hyphenated domains is not really helping the au namespace at all. New comers are discouraged and go away thinking they have missed the boat, it is too late, there is no hope, their business will fail etc. Now I am not suggesting you lie to people and say yeah some-domain.com.au is just as good as somedomain.com.au I just think putting a slightly more positive spin on things would not hurt. After all the more the value of some-domain.com.au goes up the more the value of somedomain.com.au goes up in turn. Its like real estate I guess, the more the outer suburbs rise in price the more the inner suburbs rise as a result. Having such an elitist view on domains is fine for the 1% of people that own the best of the best but for the rest of us the argument is not really productive. Again, no one denies the fact that non-hyphenated domain are the preferred choice but as we all know they are not always an option. Trying to be constructive, and encouraging new comers, would probably benefit the au domain space much more than simply dismissing everything but the best of the best as 'crap'.