Lots of people lately have been denouncing Powerpoint presentations, a term I am here using generically for slides full of bullet-point text. If you want to make or view such presentations, use OpenOffice.org, and if you have numbers to show, use proper graphs instead of textual representations.
But I want to talk about a different point. When you look at a Powerpoint, you find that quite frequently you can't understand it without the talk that went with it; it's just a collection of phrases with no indication of what they might refer to. But I've been told by several people that the four technical presentations on my website are quite intelligible from the slides alone even without my actual talk.
I have a theory about why this might be so. The bullet points on my slides are headlines, whereas the points in this wonderful parody of Lincoln's Gettysburg Address (via Language Log) are simply captions. The difference is that a headline is a complete sentences, possibly with a few omitted words, whereas a caption is just a noun phrase.
Newspapers have been around for a long time, but headlines are just over a century old: the Hearst papers pretty much invented them as part of hyping the Spanish-American War. Before that, in the Civil War, for example, war news was typically headed "The War" or some equally nondescript caption. It wasn't until early in the 20th century that the principle "The headline tells the story" was fully adopted.
Headlinese, at least English-language headlinese, isn't quite grammatically equivalent to ordinary English. Articles are often left out, and so is the copula is: headlines have to fit into a confined space across the column. It's always straightforward, though, to supply the missing words in order to reconstruct the original. When it isn't, you get the broken headlines that appear on the lower left corner of the Columbia Journalism Review home page.
One entirely modern newspaper headline did appear as long ago as 1781, however, announcing the outcome of the battle of Yorktown, the last major battle of the American Revolution. Two words told the story: CORNWALLIS TAKEN!