Facebook Inc. (FB) is clearly more than just a means of stalking your ex.

It offers popular apps including Messenger, Instagram and WhatsApp under the Facebook umbrella. But according to analysts from RBC Capital Markets, Messenger is on track to be one of Facebook CEO Mark Zuckerberg's favorite pet projects.

RBC internet analysts wrote in a note on Wednesday, June 20, that Messenger can be "highly material" to Facebook's profit and loss over time with the advent of smart, target ads within Messenger.

"Just in the last two weeks we have seen consistent ads in FB Messenger for the first time," RBC wrote, ranging from Equinox and Peloton to Georgetown University and Uber. Analysts said those specific ads appeared to cater to the interest of the research team.

"The format of the ads has also been reasonably effective: noticeable, but not overly intrusive," analysts wrote. "In our experience, the FB Messenger ads felts as natural as the FB Newsfeed ads."

There were about 1.3 billion monthly active users at last count in September 2017, RBC said, up 160% from about two years earlier. Users are also highly engaged on the Messenger platform, as a record high 47% of Facebook users now use Messenger on a daily or weekly basis.

"We view messaging monetization as one of the biggest new growth drivers across the internet," RBC wrote. "While we don't expect FB Messenger monetization to be material to FB in '18, it has the potential to be material in 2-3 years."

Analysts predicted the Messenger monetization opportunity could contribute an incremental $6 billion to $8 billion in revenue and $1 in earnings per share for Facebook by 2020, given that Messenger monthly active users can grow to 1.5 billion by that time from 1.3 billion today. That would assume about $4 to $5 in in revenue per user per year.

It's a realistic estimate, RBC said. Facebook's core platform tallied $20 in ad revenue per user in 2017, while Twitter Inc. (TWTR) monetized at $7 and Snap Inc. (SNAP) at $3 per user per year.

RBC reiterated an outperform rating for Facebook stock, issuing a $250 price target that implies about 27% upside for shares from their Tuesday close. Analysts continue to keep Facebook as their top choice in large cap internet stocks.

Facebook shares gained 0.31% in premarket trading on Wednesday. The stock has climbed about 12% since the start of the year.

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