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"There is a lot of competition in the space, not only in the U.S. but around the world. This is a continual threat," said Brian Blau, an analyst at Gartner.
From AOL's AIM to Skype and Google's Gtalk, the messaging space is nothing new and it will continue to be a tough place to compete, Blau said.
"Tech companies have been going after this for a long time. Competition is fierce because these users are highly valued and they are highly valued because they are engaged users," Blau said.
WhatsApp certainly fits the bill when it comes to having engaged users. The company boasts 450 million users each month, with 70 percent of those users accessing the app each day.
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But there are other big players in the space including Viber, Line and WeChat that could still threaten WhatsApp's market share.
"Everyone is trying in this space," said Julie Ask, an analyst at Forrester. "Google is trying, they use Google Plus and Google Chat and Facebook has been trying for awhile."
While WhatsApp may be Facebook's chance to finally establish its place in the messaging space, it's going to bring changes to the platform that may cause users to abandon the app, experts said.
For starters, the WhatsApp platform is advertisement free and charges only a $1 annual subscription fee. But the company's current business model isn't going to cut it now that it's a part of Facebook's empire, Ask said.
"Everybody seems to be just repeating what Zuckerberg said when he announced the acquisition, but there's a lot he didn't say," Ask said.