Heres a question. In some of the newspaper articles I have, t h e p a p e r s s t r e t c h o u t t h e letters in certain lines. Why is this?
EDIT: I tried to do the effect here but all the spaces were truncated. Dang.
It's called "full justified," or in some uses, "force justified." It's a text alignment technique used to place an article's text within a certain amount of page space such that the newspaper isn't left with a lot of blank white space and odd truncation of lines from word-wrapping (which you'd get from standard left-justified text; this is called the "ragged right" margin). It also provides a neater look to column-layout pages while helping conserve page space.
In books and magazines that run a full-page layout, you don't see justified text as often, but in a three-column or four-column layout (which is common in many newspapers), justified text is used more often because space is at a higher premium, and justified text often allows the page designer to fit more text into a smaller space while maintaining a neat design for a column layout.
Of course, as with many choices in desktop publishing, these decisions are going to depend on your other layout considerations - space allotted, page design, legibility, layout conventions and style guidlines, audience, print schedule and layout time, etc. (Full-justified text often takes longer to lay out, because you have to pay closer attention to word wrapping, hyphenation, and so on. Left-justified text is easier for layout designers because it can more often be allowed to wrap automatically.)