Dragging Unity Editor will pause running game?

Hi All. I am using Unity Pro 3.5.6 Windows version. Here is my question:

I created a simple level just with one AI patrolling around the scene. And my Unity editor was not maximize, so I could drag the editor to somewhere else. When I dragging the editor and not release the mouse, the game was paused. After I release the mouse in one minute, the AI didn't move at all. The same issue exists at Windows standalone build. Play the Windows standalone build in window mode, and drag the window don't let go the mouse, the game will pause. But the Web Player build is OK(drag the browser, the game will keep running correctly)

Beside, I already have "runInBackground" checked at the Player setting.

Is this the default behavior of Unity or there is some setting for this?

Many thanks!

Edward.