Those who have more questions about PS4 digital sharing check this out. Sony clarifies digital sharing. It seems primary system is the key. I am glad I will be getting games from retail. But those who are going digital read the article.

Users will be able to download and play a game on two systems concurrently, but they will need to sign in with their own account to launch the game on the secondary PS4.

At E3 earlier this year, Sony won the hearts of many gamers when it stuck it to Microsoft’s apparently restrictive game-sharing policies with its own time-tested method of sharing video games with friends.

While sharing physical copies of your games may be as easy as that, allowing friends to access your digital content is a bit more complicated. According to the PS4 FAQ, the games you purchase can be played by anyone signed in on the PS4 designated as the ‘primary system’. All the benefits of Playstation Plus such as the ability to play online will also be available to all users on the primary system. Now what if I want to allow a friend to access this content?

Here’s where it gets tricky. The game can be downloaded and activated on another PS4, but to launch it, the original buyer of the content has to be signed in on that system. So, for example, say I buy Killzone and want to share it with you. I can download the game on your system using my login details on the Playstation store. However, to launch the game, you will have to be signed in as me on your system. Seems like a lot of hassle, and it’s not yet clear whether one needs to remain signed in with the original buyer’s account after launching the game.

The current policy on the PS3 also allows for games to be activated on two systems at the same time, but one does not need the original buyer to be signed in to launch the game. Sony is taking a stricter stance on digital game-sharing this time around, probably since they see the future of distribution in the digital space. More details on the digital content policy will emerge as the PS4 edges closer to its mid November launch date.

Source: PS4 FAQ

Source: http://vr-zone.com/articles/sony-clarifies-digital-game-sharing-policies-ps4/61786.html

Sounds similar to the XB1 to me.

that sounds crappy, Ps3 allowed more.

I think we should just wait until the PS4 is released because Sony is making it sound confusing. They say that digital games can be played on more than once PS4 at once, and elsewhere you have to be signed into the main PSN account.  Like they're saying you can, but the way they're saying it sounds like you can't.

Maybe by signed in they mean you have t o have it atleast activated. Or what if that one thing they mentioned, how four PSN accounts can be signed in at once on every PS4. Maybe you can actually have the primary account of one PS4 signed into your other PS4 as a sub account while you're signed into your primary account? So that's how it'll be activated and you can still play the games.

So yeah.  I think we should wait for actual release and see for ourselves.