One of my favorite memes is tl;dr. Its very existence seems to suggest that anything that can't be condensed into a couple of brief sentences (at best) probably doesn't merit our (obviously limited) attention. I admit that over the past at least five or six years I've read the first two chapters of many books and finished reading considerably fewer. I'm also probably not even far from being alone in having read many more book reviews than the books under review themselves. But if at some point in the past we were expected to feel somewhat guilty about not devoting enough time and/or energy to reading anything longer than a few pages, the tl;dr meme suddenly allowed us to convert than guilt into pride. Maybe some people actually have the time for long reads, but if they do there must be something wrong with them. Those of us who can call upon tl;dr clearly have more important things to attend to.

So claiming tl;dr can be a sort of status symbol: You may have read the whole thing, but I only skimmed the first few paragraphs. What's more, after having done so, I'm ready to give my opinion on the entire piece, something that in the past you had to wait to do until you'd finished reading. In the comments to lengthy (that's relative, right?) articles I'll often see a short "tl;dr", but why stop there? Not having read an entire piece is no reason not to voice an opinion. So rather frequently that "tl;dr", rather than being the final word on something, serves only as an introduction to someone's take on the issue at hand.

Of course brevity is, or can be, an art, and perhaps there's also a bit of science to it. The tl;dr site gives us reviews of books in 180 characters or less, for instance Kafka's Metamorphosis:

guy wakes up, is a bug. sucks for his family.

everybody dies