Android and iOS ads go full-screen
You might not even notice it happening. The transition might be so smooth, you don't think about full-screen advertisements on your smartphone until you think back a few years. "Wait," you'll think to yourself, "did I always have to watch several seconds of video advertisement in this app, or were they added more recently?"
Apple’s iAd
Back in late August, 2014, Apple rolled out a new set of advertisement spots for developers to take advantage of. iAd Full-Screen Interstitial Banners can take the place of your entire display before an app opens or in-between sections of an app.
Pass a few levels of a free game, get an advertisement you have to watch for a few seconds, continue the game. Start up a free app and bam! There's a full-screen app.
But that's no different from what you're seeing on YouTube, right? Not really – this sort of thing HAS been implemented in-browser on desktop computers in the past. Rarely will they take your entire browser – but they can.
Google’s AdWords
Straight from Google today we're to understand that several new kinds of ads designed "specifically for mobile environments" – your phone or tablet – are coming to your Android device soon. Again, this isn't the sort of advertisement that appears in your standard day-to-day smartphone user interface. These ads appear inside apps that'd almost certainly have already had an ad elsewhere.
Mobile lightbox Engagement Ads are new to Android devices, working with HTML5 and automatically adjusting themselves to any size and shape. TrueView ads are full-screen video ads – advertisers only pay the app owner when a user chooses not to skip the video. This means you'll be able to skip – just like YouTube.
I’m still scared
Full-screen advertisements will only be inside apps, and only inside apps that you download from your respective app stores that don't get money from you otherwise. Unless you're talking about Hulu, which still plays advertisements even when you pay for a subscription – but that's neither here nor there.