Mark Hanson, a Menlo Park, Calif., real estate analyst, blogger and founder of consultancy firm Hanson Advisers, may be the only bear left in the housing market, predicting a decline of 20% in housing prices in the next 12 months.

Hanson says private-equity firms caused about 50 percent of the price appreciation in cities like Phoenix and Las Vegas, and generally overpaid by 10 percent to 20 percent, according to his calculations.

With gains of more than 35 percent since the crash for properties in Las Vegas, Phoenix and other of the hardest-hit regions, these vultures will begin to lose interest, he figures. 

However, he does not stand completely alone.

Less bearish real estate experts such as Stan Humphries, chief economist at Zillow and a Hanson fan, also see signs of froth. 

"There’s a strong distinction between a normal slowdown and the wheels coming off the housing recovery," says Humphries. "That's where I depart from Mark's take."