True. This may just be due to inaccuracies in the depth map. And therein lies the problem with synthetic aperture algorithms like this: to make it look (close to) natural, you need very clean depth boundaries. There will always be problems/artifacts when trying to calculate accurate boundaries from something as limited as a few seconds of 2D camera data.
EDIT: Hard to say if this really is a problem with the depth map. In the right image (foreground in focus), the background blur seems to end pretty close to the hair boundary, if not somewhat inside the boundary of hair - the edge of the hair appears slightly blurred. If the depth map were simply inaccurate (with the same inaccuracy applied in both images), I'm guessing you'd see a portion of sharper background outside the hair boundary. I suppose another explanation would be some biased expansion/feathering of the blur mask.
EDIT: Hard to say if this really is a problem with the depth map. In the right image (foreground in focus), the background blur seems to end pretty close to the hair boundary, if not somewhat inside the boundary of hair - the edge of the hair appears slightly blurred. If the depth map were simply inaccurate (with the same inaccuracy applied in both images), I'm guessing you'd see a portion of sharper background outside the hair boundary. I suppose another explanation would be some biased expansion/feathering of the blur mask.