Marcus has served as president at PayPal since April 2012; he took over for Scott Thompson, who departed the company for Yahoo but quickly left that job after padding his résumé with false information. Thankfully Marcus hasn't had to deal with that sort of scandal, and he's now leading one of Facebook's most important projects. His extensive background in payment technology is an obvious sign that Zuckerberg is looking to monetize Messenger. Enabling users to exchange cash payments (like Square or PayPal) could be one way to accomplish that, but it's too early to know where Marcus and Zuckerberg plan to take things. For now, it's all about scaling up Facebook's messaging products to reach new audiences. "I’m looking forward to getting my hands dirty again attempting to build something new and meaningful at scale," Marcus said. He's unlikely to get his hands on WhatsApp — at least directly — since the app will remain independent once Facebook successfully closes its pricey acquisition.