While New York-based Foursquare steals much of the headlines nowadays when it comes to the topic of location-based mobile platforms due to its remarkable growth (over 1 million members in a little over a year) and potential for real-world location-based marketing, there is an increasingly visible West Coast based startup that is quietly taking the mobile world by storm with a growth curve that actually leaves Foursquare in the dust. The company’s name is Booyah and its lead-off mobile game MyTown, a digitized twist on the game of Monopoly that lets is users “buy” real estate by checking into real-life locations, is making the world take notice. The game recently hit the staggering 2 million user mark (Foursquare has approximately 1.2 million users) and is on track to gain about 500,000 users a month!  This supersonic growth rate likely played no small part in convincing Accel Partners to recently inject $20 million into the company. So what is it that’s driving this rocket-fueled rate of growth? Earlier in the year at SXSWi we asked David Wang and Lexy Franklin that very question. Here’s what they said.