There are a couple of studies that suggest a substantial percentage -- perhaps as much as 40% -- of mobile display ad clicks are unintended or "bad" in some way. Pontiflex and Trademob are the sources of these findings.
There are a number of ways to address this. One way is changing the billing or business model (moving from CTR to CPA); another is to ensure that clicks are truly intended. For example, mobile ad networks like YP and xAd ask users to confirm that they want to actually contact an advertiser or visit the advertiser's site/landing page.
Below is an example of that approach from the YP mobile ad network:
Now Google is taking steps in its banner ad creative to make sure that clicks are valid. The company said in a blog post that
[M]ost accidental clicks on in-app image ads happen at the outer edge of the ad unit, likely when you’re trying to click or scroll to nearby content. Now if you click on the outer border of the ad, we’ll prompt you to verify that you actually meant to click on the ad to learn more.
Below are screens from the Google post. The company will require users to now click on a specific area of the banner ("visit site"). The entire banner won't be "clickable."
This is smart and together with other, similar efforts it should ensure that clicks and other consumer actions in response to mobile ads are intended and that advertisers are only charged for "valid" clicks and not fat-finger accidents.
In one sense this is a solution to a practical problem but in another it's a symbolic, confidence-building measure for mobile display advertising.