Posted By:
Fred CThis is from the PSA grading standards page:
EX-MT 6: Excellent-Mint.
A PSA EX-MT 6 card may have visible surface wear or a printing defect which does not detract from its overall appeal. A very light scratch may be detected only upon close inspection. Corners may have slightly graduated fraying. Picture focus may be slightly out-of-register. Card may show some loss of original gloss, may have minor wax stain on reverse, may exhibit very slight notching on edges and may also show some off-whiteness on borders. Centering must be 80/20 or better on the front and 90/10 or better on the reverse.
I guess it's in the interpretation of "surface wear" and "light scratch". I'm pretty sure that "surface wear" doesn't mean scuff and light scratch doesn't mean a portion of the surface is missing. A lot of us like to bash PSA and this is just the vehicle we need to start another PSA bashing thread. 
In all fairness, PSA doesn't totally suck, ask Dan McKee PSA paid him for a card they lost, ok, maybe it took a little bit of coaxing...