The move is a huge surprise: Rezab - who is sometimes referred to as "the Czech Mark Zuckerberg" - is only 28 years old.
Rezab founded the company six years ago. It has grown into one of Facebook's largest international social media marketing partners, with clients including Orange and L'Oreal. Socialbakers has received $34 million in investment funding, is valued somewhere north of $200 million, and has about 330 employees globally. More than half of the Global Fortune 500 companies - including Samsung, Discovery, Lenovo and Universal - use Socialbakers products. The company is also known for its "Engage" conferences for social media execs.
Lang and Rezab will split their new leadership duties. Rezab will focus on market education, top client relationships, and strategic insight. Lang, 43, will have a more operational, day-to-day role, including sales duties, building the company's managerial infrastructure, and expanding it internationally.
Lang comes to the company from Criteo, the publicly traded online ad company, where he was executive MD/fast growing markets (with responsibility for Scandinavia, Latin America, Eastern Europe, Middle East and Africa). Lang launched Criteo in almost 100 countries during his six years there. Criteo had about $745 million in gross revenues in 2014. Socialbakers, for comparison, books about $40 million in annual revenues, according to Business Insider's ranking of pre-IPO ad tech companies.
Prague-based Socialbakers could use Lang's experience as it grows internationally. London, New York, California and Asia are the source of most social media revenues, yet Socialbakers still has the bulk of its employees - about 235 - at its HQ in the Czech Republic.
This year, Socialbakers entered a joint partnership with Sina Weibo to create a social media insights product for Weibo's China customers. Over 100,000 people are currently using a free version.
Rezab and Lang met at the NOAH Conference about three years ago, and began talking more earnestly about a transition nine months ago.
"I am super-passionate about creating European tech companies on a global scale," Lang told Business Insider. "Some of the companies in Europe have doubtless superior tech, if not the best in the world, but somehow the European landscape lacks a bit of ambition and go-to-market, and funding and ... Socialbakers is a very good example of an exception .... it's a great product and it's going global and now is the opportunity to scale it."
Lang lives in Munich and will commute to the Prague HQ. If that sounds strange, consider the company's goals: "The Czech market is not the biggest market we have globally. ... it's going to be a lot of airplane time," Lang says.How does Rezab feel about giving up part of his control of the company he created? "Honestly and openly it makes me feel nervous but also very excited. I couldn't imagine picking a better guy than Robert. Obviously he wasn't the only guy in the process. Having kissed a lot of frogs, it's going to be in great hands. It's also an emotional moment for me because I am taking my first son to school, first grade, for the first time tomorrow morning. I'm letting my son off to school while at the same time I am moving on the company side."
But, he says, "I'm not going anywhere, right? I'll be watching it from within and helping in any way I can."
Here is the text of the official announcement:
2PM UK/3PM CET WEDS 2nd SEPTEMBER 2015
Robert Lang appointed as CEO of Socialbakers to drive the next phase of global growth
New CEO joins this month from Criteo, as founder takes the role of Executive Chairman
Prague, New York, London 2nd September: Socialbakers, the leading worldwide social media analytics and optimization company, today announced that it has appointed Robert Lang as CEO with immediate effect. Jan Rezab, co-founder of the company, will become Executive Chairman.
Mr Lang, who joins from Criteo, where he was responsible for building, rolling out and running the company in almost 100 countries during his six year tenure, will lead Socialbakers through its next phase of international expansion and product development.
Mr Lang said: "I am incredibly excited about joining Socialbakers, a company that for years has been setting the global standard for social media analytics. The team led by Jan Rezab has grown the business significantly since it was founded in 2009. Today, the company has more than 300 people, works with over 3,000 clients, and is perfectly positioned for the next stage of growth."
Over fifty per cent of the Global Fortune 500 including Samsung, Discovery, Lenovo and Universal use the company's products. Socialbakers has also recently entered into a partnership with Sina Weibo as it expanded into the Chinese market.
Mr Lang added: "I am passionate about scaling European tech companies. We have world-class technology in Europe and it is fantastic to see it matched with global ambition."
The appointment will see Mr Rezab take the role of Executive Chairman at the company he founded six years ago. He will continue to represent the company, work directly with its top clients and provide strategic input on the company's product offering that has over the years transformed Socialbakers into a leader in social media analytics.
"As an entrepreneur, I have come to recognize that Socialbakers is at a stage where it now needs someone with the experience of running and scaling a fast growing multi-national business. That person is Robert. We are confident that with Robert as CEO, the company will continue to grow rapidly as the industry leader."
In the last six years, Socialbakers has continuously led the social media analytics space with industry leading benchmarks such as its Socially Devoted, an index of companies that provide the gold standard in customer care delivered through social media channels.
The company is backed by Index Ventures and Early Bird Capital and has raised $34 million in funding in the last four years, over three rounds of investment.
ENDS
About Socialbakers
Socialbakers is the trusted partner to thousands of brands, both large and small, that successfully engage with consumers across the world. We ensure that investment in social media engagement delivers measurable business outcomes. With over 3000 clients across 100 countries, Socialbakers is the industry leader in tracking, analyzing and benchmarking social media engagement. With over 8 million social profiles across all the major social platforms including Twitter, Facebook, YouTube, Linkedin, Instagram, Google+ and VK in Russia, Socialbakers provides the gold standard for social analytics. Socialbakers has been a Facebook Marketing Partner since 2011. For more information, visit www.socialbakers.com