Not quite sure that's the question he's asking about. In the case of Pinterest, the page isn't scrollable--the image appears to be cut in half by the bottom of the page. In the case of Delicious, the image is cut off by the right side of the page. You can't scroll horizontally here. On A List Apart, the top of the title is cut off, and you can't scroll up to see the rest of it.

I think the reason for this is it gives them impression that there's a lot more to the website (even if there really isn't), by not being confined to exist entirely within the page. Also, by cutting off sections of the graphics and text, you are saving yourself a little bit of screen real estate while simultaneously doing something different and eye catching.

Just my $.02 though.