A three-dollar pair of wire cutters and a nail file and you can get pretty much anything you want. David Ortiz's toothbrush, Cody Ross' silverware, their wives and children...
No, but I agree, Ebay is notoriously unreliable for sports memorabilia. I've known many people who have ordered "Authenticated, Game-Used Equipment Signed by Players" and ended up receiving things that were obviously pulled brand-new from their packaging and scribbled on by the seller. I could print up a genuine-looking certificate, indicating that I won the International Badass Competition by defeating Bruce Willis and Harrison Ford, and I could include the authentication signature of Nelson Mandela. Anyone can do anything like that with a printer. You're better off buying from, as redsoxrules suggested, a dealer that specializes in memorabilia and has a history of providing the genuine article.