Thought the iPhone 4S’s new camera is impressive, to say the least, it does share one issue with any other camera phone or pocket digicam: the tiny sensor means it simply can’t deep focus, making the background artistically blurry while the subject is kept crystal sharp.
If you want shallow depth-of-field like a SLR while using your iPhone, consider giving Big Lens a try. It will allow you to give your iPhone photos a super depth of field, just like those fancy pants pros use.