They're expensive and they're usually mostly useless, but they sure are popular anyway! Collector's Editions are a given for any major game release these days, and MMOs are no exception -- Age of Conan
and Warhammer Online
both had 'em, and even expansion packs get 'em in Wrath of the Lich King
Sometimes they just come with fancy boxes and art work or soundtrack CDs, while other times they come with in-game bonuses like free mounts. Sometimes they even let you play the game earlier. But they're awfully pricey -- what do you think, are they worth it? Have you bought Collector's Editions before, or do you plan to? Or are you perfectly happy forgoing the frills and just getting the basic box?