"It is simply not possible to make a blanket statement that the banks are responsible for the current housing boom in Sydney/Melbourne. The people that buy the houses are. Simple. End of story. No buyers, no boom."
Yes, everyone has to be ultimately responsible under "buyer beware".
However, the banks certainly have a role in this. They did relax lending standards, no question and with interest rates going down to record lows, people thought purchases were manageable.
With prices going up and up, many felt they had to jump in or never get into a house. I have a relative and their partner worried about purchasing a family home. One is pressing more to buy, the other wants to hold back, comparing prices here to overseas.
You certainly sound like you think it is all the purchaser's fault. If a bust happens, the banks will be ruthless in getting "their" money back, the money they conjured out of very little. The banks are greedy, led by Wall Street.... why do you think the CBA has run into trouble and banks world wide are facing some $264 Billion fines for their activities, money laundering, manipulating LIBOR, running interest rates down to record levels..... to say it is solely "home purchasers" that need to take responsibility is ridiculous.