Facebook announced this week that it acquired popular messaging app WhatsApp for a stunning figure of $19 billion. The app is currently the most popular messaging app for smartphones, and boasts over 450 million users while adding an additional 1 million users every day.

Of course, not everyone that uses WhatsApp is on Facebook, and some privacy advocates have expressed concern that Facebook will now have access to all of WhatsApp’s user data.

“Currently, WhatsApp can change terms and conditions at any time, without notifying users, which many people who use this service aren’t aware of. Meanwhile, Facebook already has a very broad copyright license on people’s content and already shares your data with many other services,” said St. John Deakins, the CEO of Citizenme, a group advocating for online privacy. “Now with Facebook buying WhatsApp, this could see more and more private information becoming part of Facebook’s database. From a personal data standpoint, this is extremely worrying.”

WhatsApp will be absorbed by Facebook and function as an autonomous unit within the company. Though it’s easy to doubt the site’s motives, it’s likely that Facebook simply saw the app as a massive growth opportunity. Facebook has obvious plans to expand its messaging services, and WhatsApp is a logical extension of their goals. However, for those WhatsApp users who aren’t comfortable living under the thumb of Facebook, it may be time to find another online messaging service.