Noah Falstein has an interesting article over at Gamasutra, looking at how a selection of game designers got to where they are today — unsurprisingly, a great number displayed an interest in designing games from a young age, an obsession with rules and mechanics (though frequently on paper), and an influence from and interest in one very, very important game:
... There was one very consistent influence and theme on the early work of nearly everyone: Dungeons & Dragons. Not surprisingly, many of the people I corresponded with had been big fans of the game, and often had been drawn into design through it. There were several factors at work here: the accessibility of the game, with very wide distribution and a low starting price (particularly compared to buying a computer!), a pathway to move from player to Dungeon Master (DM) using established modules and rules, to designer creating your own dungeons and rules, and plenty of pathways from there on toother RPG's including so many computer-based variants.
The scans of early attempts at designing via pen and paper are a nice touch; the article is chock full of interesting little tidbits. It doesn't seem terribly surprising that game designers would display a propensity for game design as youngsters — unlike, say, practicing medicine, making up games is a pretty normal part of childhood, even if the designers in Falstein's piece took it a lot further than average playground hijinks. Design Language: Designer Derivations [Gamasutra]