The webinar on March 14, 2013, covered the business ROI of APIs, focusing on topics such as different API business models, branding strategies, and hackathons as promotional tools. Presenters included Leslie Hitchcock from TechCrunch, Alex Donn from AT&T, and Alex Gaber from Layer 7, highlighting the significance of marketing APIs effectively and measuring the ROI from hackathons. The discussion also addressed common challenges developers face when integrating APIs.