Aside from certain types of spam being illegal in Australia, once you have obtained the stigma of being a spammer, it takes years to shake it, and you are likely to never recover your reputation completely. It only takes the vaguest hint of spam for your business to lose customers, and rest assured, when customers think you have spammed, they won't walk away - they'll run. Most of the customers who respond in this way won't even tell you - they'll just silently activate a filter in their email software so they never see your messages, and you'll simply never hear from them again. Granted, not every customer will respond this way.
Different people do respond to things in different ways.
If you still think nobody is going to be upset by something that even has the vague scent of UBE, check out Consumer Attitudes to Privacy , a 1995 survey by the privacy commissioner. This survey was taken in what is now considered the early days of UBE, and doesn't specifically reference UBE, but it does reference many things that can only lead to the conclusion that Australians will treat unwanted email solicitations as a violation of their privacy, and will not view the sender favourably. The first quarter 1999 edition studied spam and consumer attitudes to merchants who send bulk email to them without permission. The study specifically looked at how a merchant's failure to ask up front affected the relationship with the customer. What's more, customers are now avoiding giving merchants their email address because they have already been spammed by vendors too many times.