Royal Bank of Scotland will be rolling out Facebook at Work, the enterprise version of Facebook, to all 100,000 of its employees by the end of 2016. It’s a big win for enterprise social networks, but it’s a crowded space and Facebook will have some particular challenges in winning over more companies to its business platform.

Still, it’s the biggest announcement we’ve heard from Facebook at Work in a while. Last November, Facebook announced it would release an enterprise version designed for internal corporate communications, but little has been reported since. The service reportedly went into closed beta testing in January and had over 100 companies testing it. It will exit beta and turn into a freemium service by the end of the year, Facebook at Work chief Julien Codorniou told Re/code.

This partnership could help Facebook at Work gain traction in a field packed with enterprise social networks (ESNs) like hot startup Slack, Microsoft’s Yammer, Salesforce Chatter, SAP Jam, and more.

“The more public and large-scale reference accounts Facebook at Work can muster the better they seem credible. They need more though,” said Gartner’s Mike Gotta.

That’s partly because Facebook is still coming from the consumer side and will need early adopters like RBS to provide them with the business context they are lacking.

One way this might play out is in entering industries that have regulatory or privacy requirements.

“Financial services institutions have to be careful about compliance, record retention and what constitutes authorized content on the platform to make sure it does not become a headache later and so that adoption is strong, with minor tweaks along the way,” said Harmeda technology and strategy partner Max Dufour, who also works as an interim CIO for mid-sized businesses and some Fortune 500 companies.

Along those lines, Gotta said that Facebook would do best to stay away from creating enterprise specific applications and focus on employee engagement and work with HR/corporate communications teams. Instead, they could take an “app store” style approach and partners do the heavy lifting when it comes to compliance, security, and the like.

“Facebook hasn’t demonstrated the type of insights to the world of enterprise software that involves integration with an organization’s infrastructure and application portfolio which could be a slippery hill to satisfy unique needs of regulated sectors like healthcare and finance,” he said.

Facebook’s perception problem will be still another hurdle.

“Facebook has to be somewhat ‘over the top’ in its messaging that business and employee data, info, behaviors etc. are not being handled or co-mingled with their personal world,” Gotta said.

On the flip side, making the decision to use Facebook a Work could offer the benefit of familiarity.

“Facebook at Work allows brands to ease the learning curve for employees when deploying an ESN, as it is likely the tool is something already familiar to them,” said Altimeter’s Ed Terpening.

And in general, he said, using ESNs can be seen as a way of preventing employees from starting informal networks outside the company’s firewall.

“Especially in a heavily regulated industry like financial services, businesses without an internal social network create a vacuum that may be filled by employees on their own, increasing risk to the institution,” he said.

TechRepublic will have more details on this story throughout the week as we talk further with RBS and other companies using Facebook at Work. Check back on this story for more.

For RBS, this all started early 2015. They heard about Facebook at Work and contacted Facebook, both in California and in the UK, about getting involved, said RBS’s Director of Design, Kevin Hanley.

He said they’ve tried several ESN tools in the past but haven’t found much success. Whereas with their Facebook at Work pilot program, they saw 90% adoption from those invited, similarly high rates for people continuing to use it, and interest from others within the bank about joining.

One reason Facebook at Work’s been appealing is exactly Gotta’s point about a lower learning curve.

“It’s something people are immediately familiar with, they can engage on day one,” Hanley said. (Though, Facebook and Work is totally separate from personal Facebook accounts.) And that’s important because Hanley said in the past when they’ve tried other tools, if the initial steps are clunky, then it’s difficult to generate momentum around adoption.

Another benefit they saw was the ability to use mobile. Previous solutions were mainly tied to desktop applications.

Throughout the pilot program, they set several objectives, like proof of concept–“just making sure we can stand this thing up in a safe, secure, reliable, consistent way,” he said.

When rolling it out, they didn’t prime participants to much, but rather wanted to see how bank employees used the tool naturally–without being mandated to do so–and what adoption rates were.

On broader level, Hanley said that as an organization, RBS needs to wean itself, somewhat, off email and an ESN can help with that. While email has its place, it’s more of a broadcast mechanism, he said, and an ESN can aid in engagement, interaction, and in the ability to tap into the wisdom of a 100,000-person crowd. And that’s a large benefit they’re hoping to drive out of adopting Facebook at Work.

“I think we’ve made progress against all of those dimensions to the point where we feel ready to make the kinds of announcements that we’ve done this week,” Hanley said.