Richard Green, director of USC's Lusk Center for Real Estate, believes prices are bouncing back quickly because the panic of the housing crash made them irrationally low. The increases, he said, are being driven by short supply rather than irrational buyers.
"That is something to be concerned about, but it doesn't mean there is a bubble," he said. "If prices go up another 20% in the next year, then that is starting to get bubbly."