If you need more evidence of how vitally important mobile payments have become to PayPal, take a look at the company’s new leader.

David Marcus, previously PayPal’s vice president of mobile, has been tapped to lead the company as president, eBay CEO John Donahoe announced in a blog post this morning.

Marcus hasn’t been with PayPal that long — he only joined the company last July when eBay acquired Zong, his carrier-payments startup, for $240 million — but in his short stint he’s already made his presence known. Marcus helped lead the company to $4 billion in mobile payments last year (up from only $750 million in 2010), and the company now predicts it will reach $7 billion this year. He also helped make PayPal Here, the company’s new triangular credit card reader for mobile devices (and its first physical product ever), a reality.

“He’s going to lead PayPal with that ‘founder’s perspective,’ to bring start-up energy to PayPal’s unmatched global reach and digital payment capabilities,” Donahoe wrote in the blog post. “With David at the helm, we will have an even deeper commitment at PayPal, and across eBay Inc., to be a leading technology-driven and customer-focused product innovation company.”

PayPal certainly isn’t giving up its core business of online payments anytime soon, but it’s clear that there’s a huge growth potential in mobile right now. The company has its fingers in almost every method of mobile payments — from carrier payments (it recently announced a new Carrier Payment Network), to NFC, to purchases via QR codes (using eBay-owned Red Laser). No matter which way the mobile payments market leans, PayPal wants a piece of the action.