It seems most people focused on the negative aspects of such a feature.
Yes, in most cases it would not be desirable that a website could suppress the dialog box.
But in a few cases, such as this example where he's trying to print a receipt for his business from the browser. As I understand in such a case every second is too precious to be wasted confirming potentially hundreds of receipt per day.
It's a business after all, where time is money!
There are countless other cases where one would like to suppress the dialog box, such as the eBay sellers printing their labels before shipment.
So ideally the website developer should be able to specify some basic parameters such as printer name, color/monochromatic, quality, paper size. And command the print entirely from the source coude without requiring any action from the user, except of course to configure these parameter only once.
Unfortunately most browsers aren't there yet, as their developers haven't waken yet to the full potential of hosting ALL KINDS of applications on the cloud, including applications that use printers such as POS and label printing software! By the way, here's a great niche for software as service!
The good news is that it's already possible to achieve something similar on Firefox, where you could change the browser setting to enable what they called "Silent Printing", you should set it to "Always" and you'll be good.
I'm sure IE might also have some way to do it, but I haven't found it yet.
Anybody know how's the state of printer and printing features offered by the other mainstream browsers such as Chrome and Opera?