Another related question, that would apply to invisible creatures as well: if you fail the pinpoint check, do you have any idea where they are? Perhaps you have a small area effect spell you're hoping to catch them in?
From the SRD
"A creature blinded by darkness can make a Perception check as a free action each round in order to locate foes (DC equal to opponents’ Stealth checks). A successful check lets a blinded character hear an unseen creature “over there somewhere.”
Unfortunately this appears to be pretty much GM fiat. Since I'm comfortable with arbitrary rulings I'd allow the characters success on the perception check to define a scope of area.
If one were attempting to get as RAW as possible and extrapolating the perception rules one could define each 10 ft of possible space from the target for each point by which the perception check failed by. So if you failed by one you could get within 10 ft, by two within 20 ft, and so on. By the time one hits -5 it may make more sense to simply indicate a compass direction from the character.
Personally I think that's a little harsh and would make it a diff of 3 (so on a DC of 28 a roll of 27-25 gets you in 10 ft, 24-22 gets you within 20, 21-19 gets you within 30 ft)