It's not the white space that makes the delineation, is the alignment of the items around that white space. If I plot a bunch of blocks of text on a white canvas you couldn't make columns or rows out of that mess. You'd have plenty of white space, but no delineation.

A bigger problem for me is not the visual separation, but that there are functional, but invisible, frames in the layout. The header doesn't scroll, while the left sidebar and the main content scroll separately. So, in the middle of the whitespace there's a place where scrolling changes from scrolling the left panel, to scrolling the main content.

Without the line delineation, I found myself with the mouse hovered over the left column trying to move the main content and wondering why my scroll wasn't working. If you have tall enough content in the left sidebar a (non-standard) scrollbar appears (sometimes). But if you don't have content there, or aren't moused-over the correct areas, you don't get any indication of what's happening.

If the page was a normally scrolling page with no frames, the whitespace is not terrible to me. The way the page functions, it needs the 1px frame that Google+ has.

This is even a bigger problem on small screens. On my 13" laptop I can barely see 2 contacts in the chat list and have to move my mouse over it all the time so that it grows to 5 contacts and try to scroll those.

> since when is whitespace not delineation?

When it's so low-frequency (wide) that it doesn't trigger the edge-detectors in your retina.

I laughed when I saw the massive arrow pointing to the large object that delineates the exact shape of the thing that isn't delineating anything apparently. A perfect instance of not being able to see the wood for the trees.

Not at all. Wider != more delineation.

Analogy: it's easier to cross a lawn than to scale a wall.

Edge-like features create an intensity wall in the image signal, whereas plateaus of do not.

There's a clear biological / image processing basis for this.