You knew it was only a matter of time before someone figured out a way to fill their wallets off users by annoying them to death..
I will copy and paste a reply I left about this on Reddit
I can see it now for apps like Plex when Casting goes free (whenever that happens)
"We will Cast your content right after this short advertisement"
So sick of in app ads, so sick of freemium, so sick of subscription services (ie: PlexPass etc), so sick of pay to win games, so sick of every Android developer (not every, but you get the point) nickel and diming the piss out of users either with ads or micro-transactions. Enough.. Just follow the PC software model that has worked for decades. A set price, minor upgrades are free, major revisions you re-pay. The Android software market is the biggest racket.