• by Laurie Sullivan  @lauriesullivan, June 7, 2012

Richard Alfonsi, former VP of global display sales and strategy at Google, will join Twitter Monday as its VP of global online sales.  The news announced Thursday on Twitter.

This is the fourth senior sales exec hired in the past six months. Others who joined: Shailesh Rao, VP of global revenue; Bruce Daisley, head of U.K. sales; and Stephen McIntyre, heads the Dublin office.

Twitter CEO Dick Costolo on Wednesday said the social network on many days generates more revenue from its mobile platform than it does from its Web site. The new hires in sales should help spur adoption more.

Worldwide ad revenues at Twitter grew 213% to $139.5 million in 2011, up from $45 million in 2010, according to eMarketer estimates. In 2012, the company's ad revenue should climb 86.3% to $259.9 million, the research firm said.