There is an interesting effect noted by researchers in the '40s. The eye (and visual system) is much more willing to accept out of focus closeup photos of the human face as acceptable than other out of focus content.

It has something to do with the face that as babies, with eyes that won't focus, we see close up human faces and the visual system learns to supply the missing detail. Kodak used that in the Near/Far two focus position cameras. The assumption was that closeup photos were faces and therefor a larger blur circle would be tolerated. If you were taking photos of flowers, I guess you were out of luck.