Investors shouldn't be leaving Facebook just yet, said Brent Thill, managing director of the internet research team at Jefferies.
"Clearly there's an expense hit," the analyst told CNBC before the start of Facebook CEO Mark Zuckerberg's testimony before Congress on Tuesday. Jefferies lowered earnings numbers this week.
But "a survey with our partners in the data world suggests that there's really been no major deterioration to users," Thill said on "Power Lunch." "We surveyed users last week, and they still say the dominant platform they use is Facebook with Instagram. Sixty percent use the platform more than they did a year ago. This is fresh data."
"Right now, if the users aren't leaving en masse, the advertisers won't leave," Thill said.
Facebook share prices have fallen about 11 percent over the last month in response to the Cambridge Analytica data scandal. But the stock was up about 2.5 percent at 2:20 p.m. ET, around the time the hearing was set to begin. The stock continued to rally during Zuckerberg's testimony and closed up 4.5 percent.
Jefferies analysts also talked to GDP experts in Europe. "They don't expect as big an impact maybe as Wall Street," Thill said.
"The primary fear of Wall Street is revenue growth and margins are going to deteriorate materially," he said. "We think they will deteriorate but they won't see the type of downfall that everyone is expecting."
This week Jefferies lowered earnings estimates from over $9 a share to $8.58. While Thill said short term the stock might suffer, "long term this company will ultimately grow earnings by 25 percent over the next couple of years."
And Thill said Zuckerberg's testimony before Congress is "unlikely to make issues worse."
"A lot of what's been going on has been embedded into the stock," he said.
"This is a great opportunity" for investors, Thill said.