Analyst: What's driving Facebook's growth, for now

Mobile may be the key to Facebook's growth and success at this time, but that may change soon, Piper Jaffray's Gene Munster said Thursday.

"Seventy-three percent of [Facebook's] total revenue was mobile in the March quarter; that compares to 69 percent in the December quarter. The crazy thing about this is that, just a few years ago, Facebook was [going public] and investors wondered if they would ever make money out of mobile," the analyst said on CNBC's "Squawk Alley."

The company's monthly active users (MAUs) were 1.44 billion in March—a 13 percent year-over-year rise. Mobile MAUs were 1.25 billion for that month. Both of those MAU figures topped StreetAccount consensus estimates of 1.43 billion and 1.23 billion, respectively.

"At some point, [however] we're going to reach a level where it's just not going to go any higher [and] that's probably going to be about 80 percent. Naturally, the story is going to shift into other platforms that investors are well aware of like WhatsApp, Instagram and Oculus," he added.

Munster made his remarks one day after the social media behemoth posted quarterly earnings per share slightly above Wall Street's expectations but missed in revenues.

Concerns over rising expenses? Not so much

Facebook's expenses rose about 83 percent in the first quarter. Nevertheless, Colin Sebastian of R.W. Baird said investors are not concerned about this.

"Expenses are part of the fabric for Facebook currently. They are investing near-term, intermediate-term and long-term initiatives, putting the user experience first. That's part of their strategy [and] I think investors understand that," Sebastian said on CNBC's "Squawk on the Street."

Sebastian added that a larger concern for investors is the company's exposure to currency headwinds. "The concerns on their stock are more related to currency and high expectations on the revenue side going into the quarter," he said.

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"It was magnified toward the end of the quarter, and that's part of the story for sure, but the other side of that is that advertisers in Europe spent a little less money than we expected."

Facebook's stock edged down less than 1 percent in early-afternoon trading. Click here to see where the stock is trading now.

—CNBC's Everett Rosenfeld contributed to this report.