Collectibles for the gullible

Baseball cards

Generations of kids have collected baseball cards, but in the 1980s and '90s, the hobby of amassing gum-stained pieces of cardboard really took off as speculation exploded.

So, too, did production. Manufacturers produced 81 billion cards a year during the hobby's heyday, according to the book Mint Condition: How Baseball Cards Became an American Obsession.

But the baseball card market crashed in 1994, according to BaseballNation.com, after a players' strike led to the cancellation of the World Series. The hobby hasn't recovered.

Earlier this year, Mike Berkus, executive director of the National Sports Collectors Convention, told The New York Times he estimated the amount of money from card sales has dropped about two-thirds from its peak.

There's just no demand.

This doesn't mean it's not worth your time to go through your old cards and see if you have a gem, but don't bank on it happening as a way to shore up retirement accounts.