There haven't been this many house flippers since before the housing bubble burst

There haven't been this many house flippers since before the housing bubble burst: House flipping is making a comeback, with the number of homes built on spec approaching its 2006 high. The overzealous speculation of house flippers in the months leading up to the crisis is often cited as a contributing factor to the housing bubble. So should we be worried now that houses built on spec appear to be making a comeback?