BranchOut, the professional social network, capped off a jump in users by securing $25 million in new funding led by Mayfield Fund, with participation from previous investors Accel, Norwest Venture Partners and Redpoint Ventures.

That’s about a dollar for every person who’s a registered user of the service, which is built on Facebook, and brings BranchOut’s total venture capital investment to $49 million.

The company said it will use the funds to expand its team and capabilities, which will put it in a better position to challenge LinkedIn, which has more than 150 million registered users.

BranchOut credits mobile as a primary driver of its growth, with 40 percent of new users joining via mobile devices since that became possible in February. During that same time period, the company reports an average of 2 million new registered users.

About half of those have joined from countries outside the U.S. following strategic partnerships with continental Europe’s StepStone and the U.K.’s

BranchOut founder and CEO Rick Marini said that the service was the first professional network that was useful regardless of a person’s professional status, industry or level of experience. “We power the professional profile for the Facebook generation,” he said. “We’re making it easier for our users to find jobs through their established and authentic Facebook relationships.”

Mayfield Fund managing director Tim Chang joins BranchOut’s board of directors, which also includes Marini, Kevin Efrusy from Accel Partners, Geoff Yang of Redpoint Ventures, and Stan Chudnovsky, co-founder of Ooga Labs.

Related links:

BranchOut – press release

BranchOut blog – Branchout Raises $25 Million, Surpasses 25 Million Users

Forbes – BranchOut Looks to Dethrone LinkedIn

AllThingsD – After Huge Mobile Boost, BranchOut Takes $25M More From Investors

Business Insider – Hey, LinkedIn, You’d Better Go Buy BranchOut — Before Facebook Does

Here’s an infographic Branchout created. Click here to see a larger version.