Yahoo! Chief Operating Officer Henrique de Castro has been fired after just about a year with the company. CEO Marissa Mayer issued a memo to staff on Wednesday indicating that she decided de Castro should leave the company but no reason was given for his firing. Mayer hired de Castro in October 2012 from Google. He was hired to oversee management of Yahoo!'s sales, operations, media and business development. During his tenure at Yahoo!, the company has experienced some disappointing advertising numbers and a lack of significant revenue growth.