It's been a couple of years since Facebook (NASDAQ:FB) CEO Mark Zuckerberg went all-in on both improving the mobile user experience and enhancing the site's advertising alternatives for the hundreds of millions of "friends" that access the site via a smartphone or tablet. Based on last quarter's mobile monthly average user (MAU) data, Zuckerberg seems to have struck a chord.

Mobile hasn't exactly been a friend of Google (NASDAQ:GOOG) (NASDAQ:GOOG) -- until recently. Consumers' shift to mobile devices is to blame for what many Google naysayers considered its biggest challenge: overcoming a seemingly ever-declining Cost-Per-Click (CPC) rate. However, as Google demonstrated last quarter, the steps it's taking to address the change in consumer's online usage are making a difference, and if recent data proves correct, becoming mobile-friendly couldn't come at a better time.

Setting the table
There's little doubt that Facebook and Google -- now known as Alphabet -- are the undisputed leaders in digital advertising. Of Facebook's record-breaking $4.04 billion in sales last quarter -- the first time the social media king has broken that revenue plateau -- nearly 95% was from advertising. As it relates to mobile, Facebook's stellar Q2 results are even more impressive.

Of Facebook's $3.83 billion in ad revenue last quarter, about 76% was generated from mobile spots. That figure is up from last year, in which 62% of ad sales were of the mobile variety. One look at Facebook's ever-increasing MAU growth makes it clear why so much of its revenue is being derived from mobile users.

Facebook boasts just shy of 1.5 billion MAUs; equal to about half the connected people on the planet, and nearly all of them have gone mobile. Over 1.3 billion of Facebook's 1.49 billion monthly users access the site via their mobile device.

As for Google and its renewed mobile efforts, CFO Ruth Porat summed it up nicely last quarter, saying, "Our strong Q2 results reflect continued growth across the breadth of our products, most notably core search, where mobile stood out, as well as YouTube and programmatic advertising."

It was just a few months ago that Google announced mobile search had, for the first time ever, surpassed desktop in 10 different countries, including the lucrative U.S. and Japan markets. The news of Google's mobile search wins were accompanied by an introduction to several new, mobile-friendly ad placement and measurement tools.

Like Facebook, Google recognizes that when it comes to ads, "relevancy now triumphs over brand loyalty." Meaning, mobile or not, getting the right ad in front of the right person at the right time is the recipe for success. And Google certainly knows how to collect, collate, and utilize reams of user data for its marketing partners.

How big is big?
For the first time ever, according to eMarketer, 2015 will see more digital ad spending on mobile than desktop. An expected, 51.9% of marketing ad dollars will be spent on mobile spots this year thanks to consumer's growing appetite for "non-voice" mobile usage. For example, in the U.S., eMarketer suggests that adults spend nearly three hours a day on their mobile devices for reasons other than talking. Of that daily mobile time, over half are using smartphones for reasons other than chatting.

With an estimated $30.45 billion expected to be allotted to digital mobile advertising this year, clearly there's a lot of incentive for folks like Facebook and Google to get their ducks in a row -- and the news gets even better going forward. In just four years, mobile ad spend is expected to more than double to over $65 billion. In fact, in just a couple of years, digital spots in general -- both mobile and desktop -- will surpass TV ad spend, and a growing majority of the online marketing will be directed to mobile users.

It's already a good time to be a mobile digital advertiser, and the future looks even brighter. Sure, both Facebook's and Google's stock prices have taken a hit of late -- just as so many others have -- but that's near term. Thanks in large part to their respective efforts to appease users on the go, it's no wonder both Facebook and Google have consensus price targets well above their current share prices.

Tim Brugger has no position in any stocks mentioned. The Motley Fool owns and recommends Facebook and Google (C shares). Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.