As major global tech companies like Google and Facebook gobble up office buildings and plan new construction, Twitter is bucking the trend by continuing to lease office space, albeit in the coolest new buildings around. But why the penchant for leasing rather than owning? At Twitter's fourth quarter 2014 earnings conference call held earlier this year, then-CEO Dick Costolo called the company the fastest-growing business within the $1 billion digital advertising business landscape, and said the expanding company would keep "buying" more space an option in both San Francisco and New York. However, in the midst of poor performance reports, Costolo resigned yesterday. To view Twitter's 11 rented U.S. offices, click through our gallery.