 Fans have always coveted memorabilia, but in recent years, what was once a hobby has mushroomed into big business, with millions of dollars changing hands in auctions held by such top firms as Christie's and Sotheby's.In addition, many popular films have their collectible items sold via independent, online movie memorabilia stores, web auctions, and at film studio charity events.In the early days, most people sought autographs or original photographs or posters.