Erik Johnson over at Valve has taken a strong stance against ever allowing advertisements on the Steam storefront, stating in a recent interview with GameSpot that Valve has no plans to ever sell ad space on its platform because "it would be a bad business decision, let alone just dumb."
This cements Valve's approach to games marketplace management as directly opposed to that of Sony and Microsoft, which each sell prominent ad space on their respective storefronts -- much to many users' distress.
Of course, Steam's overseers have never given any indication they intended to place ads alongside games on their platform -- Johnson goes so far as to opine that such strategies don't work for either advertisers ("I don't think anybody buys Doritos as a result") or platform holders.
The question was raised because the first official Steam Machine PCs are expected to launch next month alongside the Steam Controller and the Steam Link settop box, rendering Valve a more direct competitor with Sony, Microsoft and Nintendo for the money and time of people playing games on their living room TV.