People who don't use twitter always have the same complaint, which boils down to "you can't say anything meaningful in 140 characters." Twitter isn't everyone's cup of tea, but complaining that you can't say anything with 140 characters is a terrible excuse.
A reasonable working minimum for justified text in English is the 40-character line. Shorter lines may compose perfectly well with sufficient luck and practice, but in the long run, justified lines averaging less than 38 or 40 characters will lead to white acne or pig bristles: a rash of erratic and splotch word spaces or an epidemic of hyphenation. When the line is short, the text should be set ragged right. In large doses, even ragged-right composition may look anorexic if the line falls below 30 characters but in small and isolated patches - ragged marginal notes, for example- the minimum line (if the language is English) can be as little as 12 or 15 characters.A few paragraphs later:
On a conventional book page, the measure, or length of line, is usually around 30 times the size of the type, but the lines as little as 20 or as much as 40 times the type size fall withing the expectable range. If, for example, the type size is 10 pt, the measure might be around 30 x 10 = 300 pt, which is 300/12 = 25 picas. A typical lowercase alphabet length for a 10 pt text font is 128 pt, and the copyfitting table tells us that such a font set to a 25-pica measure will yield roughly 65 characters per line.65 characters per line? Filling two full lines would leave someone with 10 characters in change! I started counting characters on several lines throughout the book and they all yielded less than 60 characters, but each line said a lot. 140 chars might sound confining, but it's really not. Think about it as one line (or two depending on the font size) in a larger paragraph, which is part of a larger chapter, which is part of a larger book.