I've heard the "line identification hypothesis" mentioned a few times in regards to preferring ragged-right, but I'm pretty sure that's just a guess. It seems r

I've heard the "line identification hypothesis" mentioned a few times in regards to preferring ragged-right, but I'm pretty sure that's just a guess. It seems readers do find fully-justified text harder to read on the web sometimes, but I'd be willing to bet that it has a lot more to do with column width, leading and word/letter spacing. (Without appropriate hyphenation, word spacing can vary greatly in justified text, especially when lines are short-ish and words are long-ish.) I've found that a good screen-purposed serif typeface set with extra leading (1.2 em seems to be about right) and a line length of 35-40 ems works very well as justified text for "publications". Decent automated hyphenation ought to make things a lot better.