Cause gaming for dual monitor u end up using one monitor ( except other games such as supreme commander series. ). Even if u're planning to use one screen on gaming and another for surfing or watching movie. It might not be a good choice cause everything you click your browser or your movie application, the game itself will automatically minimize back to desktop. So it is quite a hassle to do so. But then if you are using for watching movie, + surfing net or surfing net + playing facebook game or photo editing. Then it is good for you.

yes it is posibble,, but every time you click on the internet browser on the other monitor the game monitor will turn into window mode..

What can i understand from ur questions is u wanted to scroll ur mouse across the game to web browser. That is not possible if ur game is FPS/RTS type as it will lock ur mouse within the screen. Correct me if i'm wrong.