Apple’s App Store has been a driving force behind the revitalized app economy ever since it first launched. According to Citibank, the App Store’s dominance won’t be slowing down anytime soon. In its U.S. Internet Stock 2011 Playbook, Citibank estimates that Apple will pull in up to $2 billion in gross revenue next year via the App Store. And if research firm Gartner’s forecasts are accurate, that number could be low. Gartner believes the global app market in 2010 totaled $4 billion, and that revenues will climb to a staggering $27 billion over the next two years. The growing popularity of smartphones is obviously seen as a major contributing factor to the exploding app market. According to Citibank, smartphone sales grew 53% in 2010 — though growth is expected to slow in 2011 to 29%.