Side-by-side: The comments that may have spooked Facebook investors

Despite a blowout earnings beat, Facebook couldn't keep the stock market happy on Thursday.

Shares of the stock fell 5.6 percent on Thursday, a move that analysts attributed in part to comments on an earnings call, where executives reiterated their views that ad revenue growth would slow in 2017.

"Some of the stuff they've said is the same things that they've said over the last several quarters: That basically, the law of large numbers is catching up to them," Gene Munster, analyst at Piper Jaffray, told CNBC's "Closing Bell" on Thursday. "I was surprised at kind of the emphasis that they put behind that — really calling out that ad load growth is going to slow. And I think that emphasis, on top of what they've said before, is what really shook investors."

Here's what David Wehner, Facebook's chief financial officer, said on Wednesday night's call, according to a transcript from FactSet (emphasis added):

"I also wanted to provide some brief comments on 2017. First on revenue, as I mentioned last quarter, we continue to expect that ad load will play a less significant factor driving revenue growth after mid-2017. Over the past few years, we have averaged about 50% revenue growth in advertising. Ad load has been one of the three primary factors fueling that growth. With a much smaller contribution from this important factor going forward, we expect to see ad revenue growth rates come down meaningfully. Secondly on expenses, though it is premature to provide specific expense guidance, as Mark mentioned, we anticipate 2017 will be an aggressive investment year. Adding top engineering talent remains one of our key investment priorities as we continue to execute on our 3, 5, and 10-year roadmap. We will continue to invest in our ability to recruit top technology talent, both in the Bay Area and beyond. In addition, we expect to grow capital expenditures substantially, as we continue to fund the ongoing data center expansion effort that we have underway."

Here's how that wording compares to Wehner's comments on a July conference call, according to FactSet's transcript:

"Turning now to the outlook. First, some color on revenue. We have been pleased with the strength of our advertising revenue in the first half of 2016. As I discussed on our last call, while we expect the main drivers of our advertising revenue growth will continue throughout 2016, we will face tougher comparables as the year progresses, given the accelerating revenue growth rates we experienced in the second half of 2015. Consequently, we anticipate lower advertising revenue growth rates in each successive quarter in 2016. Additionally, we anticipate ad load on Facebook will continue to grow modestly over the next 12 months, and then will be a less significant factor driving revenue growth after mid-2017. Since ad load has been one of the important factors in our recent strong period of revenue growth, we expect the rate at which we are able to grow revenue will be impacted accordingly. Turning now to expenses. Based on our updated view of the remainder of the year, we are tightening our expense guidelines ranges....We are investing across our infrastructure to prepare ourself for growth across all of our different services. And part of that investment is really to support video. That is definitely more taxing on the network and we're investing heavily on the network side..... We do expect that ad load will be a less significant factor driving overall growth, especially after mid-2017. The optimal ad load is really a mix of art and science. We've carefully tracked the impact of ads on the user experience over the last several years. We aren't seeing a cause for concern. We also want to be thoughtful about making sure that each person's overall feed experience has the right balance of organic and ad content. And that factors into how we think about ad load and where that might ultimately be. And that's really why we're talking about our expectation that as you get into mid-2017, ad load will not be a big factor in driving overall inventory growth."

Despite a strong reaction in the markets, analysts are still largely bullish on Facebook's stock.

"While there was a set of commentary about 2017 could give some pause, at the end of the day this is a company that tends to be very conservative in the way they talk about forward trends," UBS analyst Eric Sheridan told CNBC's "Squawk Alley" on Thursday.

Mizuho Securities analyst Neil Doshi told "Squawk Alley" that he'd reviewed transcripts for the past four years looking for the company's word choice.

"Every year they've used the words 'meaningful investment' or 'significant investment.' And every year they've come out with a set of operating expense guidelines, and they've always done better than what their initial guide was," Doshi said.

Morningstar analyst Ali Mogharabi told "Closing Bell" he's modeled 30 percent top-line revenue growth for Facebook over the next five years, still an "impressive" figure for a company.

"But you know, I think the reaction indicates just how different that is — if it turns out to be correct — from how they've been growing the last three years, which has been an average of 52 percent a year."

Though Facebook said ad load growth might slow on its flagship site, Munster said there's still room to grow ad load on Facebook's other properties, like Instagram, WhatsApp and Messenger.

"This is a growth story and I think some investors have been a little bit shaken on the growth," Munster said. "We're still optimistic because we think there are several levers they can still optimize over the next several years."