There have been many estimates. Generally what you see is that a lot of financial institutions just pay it out. There isn't one steadfast number out there. In Alberta, the real estate fraud committee reported that there were 2,750 incidents of real estate fraud for one year, in 2008. Based on that estimate, I've seen anything upwards of between $1 billion and $3 billion in terms of real estate fraud.
On October 5th, 2009. See this statement in context.