Yesterday, plenty of PlayStation 4 users stumbled across Destiny in their game library. That's unusual considering that they don't actually own Destiny. Is this some sort of free trial? Maybe, fingers crossed, a mistake on PlayStation's behalf?
Nope, it's just the newest way that Sony's advertising to you.
Upon clicking through, instead of launching Destiny it took everyone to a store where they could buy Destiny. It's called "featured content" by Sony. Basically, PS4 will put things that it thinks you will like front-and-center like this, right alongside all the games you actually own. Given PlayStation's stakes in this particular title, it's easy to see why the platform-holder might think that everyone is interested in the moon shooter.
If this type of advertising doesn't sit well with you, here's a bit of good news: It's simple enough to turn off. In the settings menu, navigate to "system," go to "automatic downloads," and uncheck the box that reads "featured content." There will still be plenty of other ads on your console, but none that disguise themselves as games you already own.