Battle of the tech titans: Ellison vs. Benioff by Fortune Editors @FortuneMagazine November 28, 2011, 10:20 AM EST E-mail Tweet Facebook Google Plus Linkedin Share icons FORTUNE — Fierce competitors need, well, fierce competitors. The latest smack-down? Oracle ORCL billionaire CEO Larry Ellison vs. Salesforce.com CRM billionaire CEO Marc Benioff. Benioff once worked for Ellison, who later invested in Salesforce.com, the cloud-computing software company. No matter: Now the two battle for customers — as well as bragging rights as the world’s most visible software mogul. The rivalry is getting testy: Recently Ellison canceled Benioff’s keynote at the Oracle Open World conference. This article is from the December 12, 2011 issue of Fortune.