Posted By:
Eric BrehmPaul, point well taken. For one thing, I think the grading companies are too liberal with their allowances for centering, at least according to my tastes. In most cases I would prefer a well centered '5' with a little honest corner wear than a grotesquely centered but sharp-cornered '7'. For this and other reasons, I do not buy graded cards sight unseen. And I have found that most eBay sellers and auction houses are willing to send higher quality scans when the ones in the auction listings are too small to discern adequate detail.
Of course, another important aspect of grading is authentication, i.e. verifying that a card has not been altered, but that is a whole subject unto itself, which has been widely discussed here (to say the least).