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Despite the impressive display of animal spirits inherent in Facebook's (META -0.28%) $19 billion acquisition of messaging application WhatsApp, U.S. stocks are slightly higher on Thursday morning, with the benchmark S&P 500 and the narrower Dow Jones Industrial Average (^DJI 0.34%) up 0.12% and 0.17%, respectively, at 10:15 a.m. EST.

Facebook stunned the technology industry yesterday afternoon when it announced that it would acquire the low-profile -- but highly popular -- messaging app for $19 billion in cash and stock, making it far and away Facebook's largest acquisition to date.

WhatsApp's usage statistics are astounding: It claims 450 million active users (with an extra million signing up every day), 72% of whom use the service on a daily basis. The number of messages that flow through its system is thought to be roughly equal to the total volume of SMS messages. All the same, there are a few things that don't seem to add up with this megadeal:

WhatsApp's approach to user data is the exact opposite of Facebook's
As Jim Goetz, writing on behalf of Sequoia Capital -- WhatsApp's lone venture capital investor -- noted in a blog post:

WhatsApp does not collect personal information like your name, gender, address, or age. Registration is authenticated using a phone number, a significant innovation that eliminates the frustration of remembering a username and password. Once delivered, messages are deleted from WhatsApp's server. It's a decidedly contrarian approach shaped by Jan's experience growing up in a communist country with a secret police. Jan's childhood made him appreciate communication that was not bugged or taped.

Where Facebook wants to know as much about its users as possible, WhatsApp only wants to know their phone number. As such, their business models look completely incompatible. To Facebook CEO Mark Zuckerberg's credit, he appears to recognize this and will not try to transmogrify WhatsApp into an advertising-driven application.

Instead, WhatsApp will remain autonomous and ad-free; on a conference call yesterday to discuss the deal with analysts and investors. Zuckerberg said, "I don't personally think ads are the right way to monetize messaging systems." Nevertheless, this raises the question of whether WhatsApp will ever be able to monetize its user base in a manner that would provide a return on the acquisition price. But, then, as WhatsApp CEO Jan Koum said on yesterday's call, "Monetization is not going to be a priority for us. We're focused on the growth." The stark difference between these business models raises another question:

Is this acquisition driven by opportunity or fear?
It's pretty clear that Facebook views any company involved in the social networking and mobile application spaces growing at WhatsApp's rate as a legitimate threat to its business. In this industry, the power -- or the perception of power -- appears to lie with the up-and-coming disrupter, rather than the dominant player.

That's is the sentiment behind Zuckerberg's comment that "WhatsApp had every option in the world, so I'm thrilled that they chose to work with us," and it explains the exorbitant price Facebook was willing to pony up in order to seal the deal. While that is a wonderful dynamic for WhatsApp's employees and investors, it raises an uncomfortable question for Facebook shareholders, or as the Financial Times' Robin Harding tweeted yesterday:

It seems like social networks are terrified of disruption (hence $16bn for WhatsApp). But in that case, what justifies their valuation?

— Robin Harding (@RobinBHarding) February 20, 2014

The more I learn about WhatsApp, the more I'm impressed by the company and the more I'm convinced that Facebook took the right messaging application out of play. However, I'm also convinced that the deal will never prove economic for Facebook and it illustrates that Facebook's executives are less certain of the dominance of the franchise than their shareholders.