Mark Zuckerberg and Jack Dorsey's 'Silicon Valley billionaires club' just invested in this customer service startup

Facebook founder Mark Zuckerberg, Facebook COO Sheryl Sandberg, LinkedIn founder Reid Hoffman, and Twitter founder Jack Dorsey have their own secretive private venture capital firm. It's called ICONIQ Capital, and it just invested in a San Francisco customer services startup called Intercom.

Launched in 2011, Intercom bills itself as a "customer communication platform on a mission to make internet business personal." That translates into a number of products designed to help customer service providers work more efficiently and effectively.

The company just raised $35 million (£22.6 million), it announced on Wednesday, with the series C round led by Iconiq, along with participation from previous investors The Social + Capital Partnership and Bessemer Venture Partners. (We first saw the news on Independent.ie.)

Iconiq is like a venture capital firm like no other. A December 2014 Forbes article by Brian Solomon described it as "'Zuck & Friends' secret billionaire fund." As well as Zuckerberg and Sandberg, Facebook-affiliated clients include cofounder Dustin Moskovitz and early employee Sean Parker, along with Twitter's Jack Dorsey, LinkedIn's Reid Hoffman, and Dropbox's Drew Houston - plus a number of other non-tech billionaire investors.

The fund is headed by Divesh Makan, a former Goldman Sachs investor, and previous investments include SurveyMonkey, DocuSign, GoFundMe and Flipkart. Now Intercom is being added to that list.