Facebook stock popped more than 7 percent on Wednesday on analyst comments that the social network is seeing strong demand from advertisers setting up what could be a robust year.

SunTrust Robinson Humphrey's Bob Peck reiterated his "buy" rating and $70 price target in his recent note. He also recommended investors add to their positions and take advantage of the recent 20 percent pullback.

On CNBC's "Fast Money," Peck said that he thinks the real reason the stock was up was a call SunTrust held with Nanigans, Facebook's largest preferred partner, which explained that "it looks like the numbers are going to be better than people think."

"One of the greatest concerns is ad loads. Are they getting the numbers by shoving too many of the ads in front of you? So the fact that ad loads were stable and pricing was up is a big driver. And what's really driving that underneath are the ROIs," he said.

Read MoreWho's winning the cloud wars? Not who you might think

The social network announced Wednesday afternoon that in the coming months it will be rolling out a new larger design for ads in the right-hand column. While the ad size will increase comparably to the size that appears in the News Feed, Facebook will also be reducing the total number of ads.

Watch the interview with Robert Peck, SunTrust Robinson Humphrey managing director.