Now, Facebook is actively encouraging companies to bring their customer service experiences to the platform.
"The one thing I really want to get rid of is the need for anyone to ever have to call a 1-800 number again," Marcus said.
On Tuesday during Advertising Week in New York, the Messenger team unveiled new Objectives, which are advertising goals brands can use to customize conversations using their chatbots. For example, a company could ask Messenger to help it reach more customers or get people to increase traffic to its page and the company will help it craft its chatbot to reach that goal.
"That's my personal crusade," said Marcus. "If we can over the next three years build a habit of people to search on Messenger for businesses they need to interact with, create all kinds of entry points outside of Messenger to bring in those people, and the experience is so much better than a 1-800 call or email or any of the other ways of communicating with businesses, I think that would be a huge transformation for people."
Younger users haven't yet become accustomed to telephoning companies for customer service, and Messenger can help train them toward using chat first, Marcus pointed out.
Telephoning "is not what (young people) want to do," he said. "The way they communicate with friends, it's not like they're calling them anymore. They're just chatting with them all the time on Messenger and other platforms."
The messaging experience can save time and create a better experience for customers, as well as lower costs for companies, he said.
For example, T-Mobile is using Messenger to get more customers to buy the new iPhone and sign up for a new plan. The company runs customer support, new customer acquisition, and iPhone purchases through Messenger. It has integrated a Messenger extension that provides an explanatory video about the new phone's features. Clicking on the video to learn more leads directly to a Facebook Messenger chat with T-Mobile. T-Mobile claimed it was able to get seven times more users to sign up with them on Messenger than when it directed people to its website.
Creating company-led experiences for Messenger is free, Marcus said. But if it can convince companies to build on Messenger, more people will use the app and more brands will buy advertising to direct customers to the app experiences.
Facebook's other messaging app, WhatsApp, has different markets where it is most successful — India and Latin America, particularly — but Marcus says the two business units "share the same goal, and the approach is similar."
"Ads has done quite well for us as a company," Marcus said smiling. "I think we'll continue on that trend."
Disclosure: NBCUniversal parent company Comcast owns Fandango.