Next year is predicted to be the one when overall mobile ad spending will surpass that of desktop ad spending, but now it seems something else significant will happen even sooner. Mobile programmatic display ad spending will account for 60.5% of total U.S. programmatic display ad spending this year, with $9.33 billion, surpassing desktop's share of programmatic for the first time, according to a new report from eMarketer.

Mobile advertising has been a big topic of discussion lately, in part because of the fears that mobile ad blocking will catch on with consumers, a fear that has been growing since Apple announced earlier this year that it would enable content blockers -- including ad blockers -- on its mobile Safari browser.

Marketers are otherwise trying to figure out the best way to approach mobile in general, and in light of the ad blocking fears, many are developing strategies beyond the mobile display ad, which risks getting blocked by blockers.

Even so, it appears it won't prevent them from spending on mobile display ads. According to a recent survey conducted by Ad Age and RBC Capital Markets, 71% of marketers are spending on mobile, with 36% of marketers allocating over 10% of their online budgets to mobile. Survey respondents also said that they believe mobile has the biggest opportunity to increase programmatic spending.

Not surprisingly, Facebook is playing a role in the rise of mobile programmatic, said eMarketer, considering Facebook is a "largely programmatic platform" and its U.S mobile revenues are expected to reach $5.89 billion this year and reach $10.32 billion by 2017.

In some ways Facebook may play a more secondary role in the growth of mobile programmatic ad spending, eMarketer said, "as both mobile web and app publishers increasingly look to redesign their sites in the style of Facebook's popular in-feed units."

But that doesn't mean that Facebook's role will dwindle. Clarifying that, Lauren Fisher, programmatic analyst at eMarketer, said in an email: "eMarketer is NOT saying that publishers adopting in-feed units means a reduced role for Facebook. What we are saying is that the popularity and success of these types of units on Facebook will fuel their growth and adoption on other sites and with other publishers. In the long run, this will actually probably be a good thing for Facebook."

For what it's worth, 80% of Facebook's mobile ad network inventory is native ads, which includes in-feed ads, according to Facebook.

Video ads, of course, will also play a role in all this, as eMarketer expects video to have "swift growth" over the next two years, but that's in part because it's not a huge portion of the programmatic spend right now. Video mobile programmatic will reach an estimated $1.14 billion in 2015, and that number will reach $3.79 billion by 2017, yet it will still only account for 18.5% of the U.S. mobile programmatic display ad spend.

Programmatic advertising still faces a number of challenges, including inventory quality and viewability.

Mobile advertising has its own set of problems that can help contribute to ad fraud, including the fact that location data isn't always accurate, and that the software cookies that help track web surfers on desktop computers can't follow users from app to app. Efforts to counter that or at least give marketers some help include the Mobile Seller Trust Index from anti-ad fraud firm Pixalate, which describes the index as an independent, standardized rating system of ad exchanges' fraud activity. According to the ranking, Amobee and Rubicon Project were the least fraudulent mobile ad networks.