Google is making the move to ensure most of the advertisements running through YouTube, Google Display Network, AdMob and Doubleclick will be served securely.  Google as outlined their targets for moving ads to HTTPS from HTTP.

They announced it as part of their HTTPS Everywhere mission, which has seen things such as a small search ranking boost for websites using HTTPS.

• We’ve moved all YouTube ads to HTTPS as of the end of 2014.
• Search on Google.com is already encrypted for a vast majority of users and we are working towards encrypting search ads across our systems.
• By June 30, 2015, the vast majority of mobile, video, and desktop display ads served to the Google Display Network, AdMob and DoubleClick publishers will be encrypted.
• Also by June 30, 2015, advertisers using any of our buying platforms, including AdWords and DoubleClick, will be able to serve HTTPS-encrypted display ads to all HTTPS-enabled inventory.

Of course we’re not alone in this goal. By encrypting ads, the advertising industry can help make the internet a little safer for all users. Recently, the Interactive Advertising Bureau (IAB) published a call to action to adopt HTTPS ads, and many industry players are also working to meet HTTPS requirements. We’re big supporters of these industry-wide efforts to make HTTPS everywhere a reality.

The significantly smaller ad inventory that is being served as HTTPS through Google AdSense has resulted in many AdSense publishers not switching their own sites to HTTPS, as many reported significant loss of AdSense revenue, with some switching back to HTTP until ad inventory increased.  This will make a huge difference for those publishers who were sitting on the fence about going to HTTPS, simply for the revenue concerns.

With both Chrome and Firefox encouraging webmasters to switch to HTTPS through either warnings or deprecation, there will be increased pressure for webmasters to make their sites secure.