It happens all the time. Its hard to tell with photos unless too much has been taking off. The easiest way is to compare the size of the card. BGS have soem backdoor deals me thinks and certain sellers have proven to be trimmers with favourable grading and caught out. Unfortunatley those threads get deleted by Beckett of course :evil:
Shoeless-joe is one eBay seller to stay clear of. Look at all those gold labels and trimmed cards! :shock:
It doesn't seem to happen as much with vintage as it does some of the more expensive or low pop report modern cards. I have yet to get a trimmed vintage card.