I've seen a few of these around and I love the effect.
I'm a developer, but proficient with basic Photoshop. I've played around with masking an area and entering the text within but it never formats right, so I assume this is done very carefully by hand or there's a better way?
I've also seen images of this style but inverted (the text makes up the image content, not the background).
Thanks if anyone can give some insight in advance!
Edit: To clarify, the image is made up completely of text lines. Formatting/coloring creates the actual image within this massive block of text.
Edit 2: Updated with another closeup example. You can see how the text actually wraps the full page, yet breaks to give space for the design before continuing.