While there have been reports of Australians being duped in such a way, the problem here doesn't seem to have reached such a critical mass. However it may well happen in time.
One thing I have noticed when I look at my stats is that there are usually a few visitors coming from Ghana and Nigeria each day looking for Aussie dating sites. These are the two countries where most of these scams originate, so clearly a fair proportion of these visitors are fraudsters looking for sites to target.