What happened

Shares of Facebook (META -5.61%) stock slipped a modest 0.2% early this morning. Don't worry, though. They got it back and in fact are up 1.2% as of 3 p.m. EDT.

What's more interesting is why Facebook shares dipped in the first place -- and how this is connected to a 0.7% gain in Apple (AAPL -2.88%) stock and an even bigger 4.5% pop for Roku (ROKU -10.47%).

Red arrow goes down and green arrow goes up.

Image source: Getty Images.

So what

Turns out, Facebook suffered a downgrade this morning when analysts at Rosenblatt cut their rating on the shares from "buy" to just "neutral." Facebook, you see, has long been seen as one of the most dominant forces in digital advertising on the internet. But as StreetInsider.com reports, Rosenblatt believes that the tide is turning as advertisers shift their focus increasingly toward reaching "Gen Z" with their advertising dollars.

The analyst forecasts that by 2022 the digital advertising market will grow by $50 billion in value, but only $20 billion of this will go to Facebook, while $30 billion is spent on its competitors' platforms. The analyst then proceeded to explain why, in Rosenblatt's opinion, companies like Apple and Roku will be primary beneficiaries of this trend. Amazon.com (AMZN -2.99%), too, is expected to benefit by stealing as much as 470 basis points-worth of the digital advertising market from Facebook.

Now what

Big picture: Facebook is still growing -- and an extra $20 billion in advertising next year is hardly chickenfeed. This, I believe, is why investors who instinctively began selling Facebook stock on the downgrade news quickly reversed course and began buying the shares back.

That being said, the primary import of Rosenblatt's report is that even if Facebook is getting bigger, the "still accelerating" growth in Amazon's advertising business and the fact that "Apple advertising is no longer dead" make these two stocks even more attractive prospects. At the same time, the analyst has highlighted Roku as a stock with a "long runway" for future growth off of its current "1%" market share of the U.S. advertising market.