As a former authenticator for one of the biggest company specialize in authenticating authographs of celebrities and sport athletes, I come to realize ebay have a big problem on their hands trying to figure whether a seller is selling a real autograph or fake. I will put it at 90% are fake in the ebay market today. Even if the item has been graded by PSA/DNA, some are forged so good that they still pass.
I was looking at ebay seller tmoney8484 He's a top-rated seller. You guess if he's a top seller that he's a good seller to deal with. To be a Top-rated Seller you need to sell at least 100 item and $3,000 dollars worth. Seller been on ebay since 2003. So he got about 8 years of experience to fine tune his craft. A lot of the items he sale come with a proof photo. It really doesn't mean much other than a person signing a particular item in the photo. Does the proof photo match the item the seller is actually selling? If not, the seller probably got it off the internet from somebody else.
Next he have videos. But there are drawbacks. Most of the videos I seen so far are of celebrities signing random items from fans or show the star in front while he hold the autograph item as the video is rolling. I'm 100% sure he just show up at these signing event with the item already signed by himself. Yes, he FORGE majority of their autographs except some of PSA/DNA. The kid is clever. He did his online homework and go where the celebrity is at.
He mention on his ebay auction "Don't be fooled by fakes on eBay. If it seems too cheap or too good to be real, it probably is a fake." In his case, all he's doing is jacking up the prices.