With smartphone usage skyrocketing in key global markets, one thing is clear: mobile is the future, and the future is here.

Not surprisingly, everyone is rushing to capitalize on the significant opportunities that mobile is creating.

Publishers are trying to make sure they have attractive mobile offerings that produce compelling mobile ad inventory that advertisers are increasingly looking to snap up.

In many cases, that’s easier said than done. Some of tech’s biggest names, like Facebook, are struggling to crack the mobile monetization riddle. Upstarts like Instagram and Viddy have figured out how to build great mobile experiences, but haven’t yet proven that they can supply advertisers with great mobile ad opportunities.

While there’s little doubt that somebody will figure out how to make big money from mobile ads, it is also quite clear that there are significant challenges standing in the way.

Accidents happen

If advertisers are going to feel comfortable pouring more money into mobile ads, the biggest challenges publishers and advertisers may face are the fat fingers of their users.

That’s according to a recent study by app marketing platform Trademob, which found that some 40% of clicks on mobile ad were “completely worthless.” In looking at 6m clicks across 10 mobile ad networks in June, Trademob concluded that 22% of these worthless clicks were the result of accidents.

It’s a phenomenon that seems to be universal. As detailed by AdAge, Facebook is currently working to deal with the problem of fake ‘Likes’, a scourge that threatens Facebook’s relationship with advertisers, many of which count ‘Likes’ as an important social KPI. But, as AdAge’s Cotton Delo humorously writes, Facebook “can’t do anything about fat fingers” — fat fingers that Facebook admits are becoming more of an issue given the rise in mobile usage of the world’s largest social network.

Fat fingers can’t cover up bad metrics

On one hand (no pun intended), inadvertent clicks are a huge mobile challenge. On the web, advertisers frequently pay by the click. Yes, they have to deal with fraud and individuals who count clicking on ads they don’t care about as a favorite pastime, but fat fingers aren’t really an issue. On mobile, the number of unintentional clicks appears to be so high that it might, in some instances, call into question the viability of pay-per-click model altogether.

But does this really matter? As a measure of campaign effectiveness, most experienced advertisers ditched the notion that the ‘click’ was an exceedingly meaningful metric long ago. No, it’s not entirely useless, but for most advertisers, it’s what happens after the click that matters most.

With this in mind, it’s clear that mobile really isn’t changing the game. So long as advertisers spend on campaigns that drive actions directly tied to ROI, and not simply for clicks, their mobile ad campaigns will be successful, fat fingers and all. And for those that don’t? Their wallets may become a little less fat.