General Question To Architecture Design Of Modern Websites

We want to build a website, which interact with database and and server side business rules only with REST WebServices. So if we want to build a mobile app later, the app can simple use these WebServices. So we thought we will use Yii to build the database layer (+ business rules), made only of REST WebServices. In the frontend backbone.js interact with the REST WebServices to get data.

Is that a good idea with regard to performance and security? How big sites and apps handle the interaction between frontend and database layer nowadays?