In Slate, David Jamieson has a terrific article on what happened to the once-booming market in baseball cards. It turns out that the market peaked in the early 1990s, and now cards aren't worth nearly what they used to be worth. I can certainly relate to this excerpt (although I would have been the newbie collector in the story):

  When I was a kid, you weren't normal if you didn't have at least a passing interest in baseball cards. My friends and I spent our summer days drooling over the display cases in local card shops, one of which was run by a guy named Fat Moose. The owners tolerated us until someone inevitably tried to steal a wax pack, which would get us all banished from the store. Then we'd bike over to the Rite Aid and rummage through their stock of Topps and Fleer.
  Card-trading was our pastime, and our issues of Beckett Baseball Card Monthly were our stock tickers. I considered myself a major player on the neighborhood trading circuit. It was hard work convincing a newbie collector that Steve Balboni would have a stronger career than Roger Clemens. If negotiations stalled, my favorite move was to sweeten the pot by throwing in a Phil Rizzuto card that only I knew had once sat in a pool of orange juice. After the deal went through, my buddy wouldn't know he'd been ripped off until his older brother told him. He always got over it, because he had no choice: Baseball cards were our common language.

Looking on the bright side, now is a pretty good time to pick up that Mickey Mantle or Ted Williams that you always wanted when you were a kid.