What Facebook isn't saying about its WhatsApp purchase

Facebook's $16 billion (or $19 billion by some measures) purchase of WhatsApp doesn't mean it has won the mobile messaging wars just yet, industry experts say.

(Read more: Is Facebook's acquisition of WhatsApp a desperate move?)

WhatsApp faces serious competition and is going to have to make some changes if Facebook is going to turn a profit from the deal, analysts said.

WhatsApp app on phone with Facebook logo.
Chris Ratcliffe | Bloomberg | Getty Images

(Read more: An outrageous price for WhatsApp? Hang on ...)

"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.

(Read more: WhatsApp: Sequoia's second big Facebook app deal )

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.

One big thing Zuckerberg didn't mention was that the company bought WhatsApp because it gives Facebook access to a wealth of user data, which opens up both data mining opportunities, and possible privacy concerns, analysts said.

"The data side of the story sounds creepy, it's not PC to talk about, it's not cool. People might start talking about privacy," Ask said. "I don't know what company would come out and say 'we are collecting all your data.' "

That's what's happening with this acquisition, analysts said. Even if Facebook doesn't look at a person's raw data, the company will find a way to make money off it.

"These are really platform plays. This is about how many minutes a week or a day a customer spends on your platform. It's about collecting that data and monetizing that data and becoming a destination for consumers," Ask said. "Someone would be crazy to have 450 million users and not collect data and generate insights from it."

The fact that Facebook will have access to conversation data may lead some users to abandon WhatsApp, said Nico Sells, CEO of the messaging app Wickr and an organizer of Defcon, a hacking conference.

"I always look at it from the perspective as to what's in the servers and they are sitting on a big set of data and Facebook will utilize that," Sells said.

"WhatsApp's privacy policy is not great, but it's not nearly as aggressive as Facebook's. So privacy issues will get worse."

WhatsApp's new billionaires
WhatsApp's new billionaires

Besides cashing in on users' data, Facebook may also try to force advertisements onto WhatsApp, which would run the risk of pushing users away.

On Wednesday, Zuckerberg said that Facebook didn't see advertising as the way to go when it comes to making money from WhatsApp. Instead, he said that the company would focus on growing its users and figure out how to make money later.

But there's a good chance that the same thing that happened to Instagram will happen to WhatsApp said, Ask said.

"I'm not in Zuckerberg's head, but I'd say advertising is coming because not trying to make more money isn't typically how businesses run," Ask said.

Jan Koum, a co-founder of WhatsApp, reiterated this sentiment in a company blog post on Wednesday stating "you can still count on absolutely no ads interrupting your communication."

But it's unlikely he'll be able to keep his word, Blau said.

"They can't possibly be serious about that," he said. "They are going to keep it that way for as long as they can, but its going to happen one way or another."

By CNBC's Cadie Thompson. Follow her on Twitter @CadieThompson.