Twitter Proves Its Worth as a Killer App for Local Businesses New Orleans Pizza Joint, Chicago Yogurt Chain See Results From Promos on Microblogging Service NEW YORK (AdAge.com) -- All those brands trying to figure the ROI of Twitter? They might do well to follow the lead of the local pizza joint. NAKED PIZZA: Recent Twitter promotion brought in 150% of a recent day's business. Naked Pizza, a New