Facebook CEO, Mark Zuckerberg Matt McClain | The Washington Post | Getty Images

Facebook shareholders wiped more than $130 billion off the company's market value Wednesday after the company's second-quarter earnings call. Shares fell as much as 24 percent, slumping below $170 in extended trading. The call and subsequent plunge followed a revenue miss for the company and a report of lower daily active user counts in Europe. The stock came back a bit in premarket trading Thursday, off by 17 percent. The company's top executives delivered a few scary warnings:

Revenue deceleration

Chief Financial Officer David Wehner said shareholders can expect "revenue growth rates to decline by high single-digit percentages from prior quarters" for the third and fourth quarter.

"We plan to grow and promote certain engaging experiences like Stories that currently have lower levels of monetization, and we are also giving people who use our services more choices around data privacy which may have an impact on our revenue growth," said Wehner. He also said currency fluctuations would hurt the stock in the second half of the year, after helping it for the last several quarters.

Weaker margins

Wehner also said the company expects margin compression, with operating margins trending toward "mid-30s on a percentage basis," compared with second-quarter operating margins of 44 percent. That tightening is the result of broadening markets, investments in news products — such as the recent introduction of the company's long-form video format, IGTV — and capital expenditures related to safety and security that total "billions of dollars," Wehner said. "We think that's the right thing to do for the business in terms of ensuring the community, safety and durability of the franchise," he said. "But they don't have obviously immediate translation into revenue dollars."

Effects of privacy changes