Los Angeles-based Rubicon Project announced today that the firm has expanded into the UK, and hired on Jay Stevens as Vice President and General Manager, International. Rubicon, which provides online advertising optimization for web publishers, said that Stevens joins form MySpace, where he was SVP of Audience and also VP of MySpace's European operations. As part of the hire, Rubicon said it has opened up a new office in London. Stevens has also previously served at Silverpop. Rubicon is venture backed by Clearstone Venture Partners, Mayfield Fund, and IDG Ventures.