Even before 2008 it's an issue. I bought in 2008 and cash offers were still preferred over 20% down, which was preferred over less than 20% down. It's because when you make the purchase agreement, the buyer can get a bunch of outs, many of which are based on financing not getting approved. The more difficult your financing situation, the more chance there is of it falling though.
Did you mean geographically? Or temporally? because if the second, I'm pretty sure that is a direct legal consequence of the 2008 housing meltdown that boned both sides of the lending equation.