Once again someone makes my point for me better than I did! And, in any case, I can quite happily read your comment below this editing window even though it occupies around 80% of the screen width of my admittedly small monitor.
People seem to forget that observations about the readability of wide columns of text are accompanied by recommendations that do not simply end with "restrict the width to ten words". Such recommendations came about through centuries of experience with the printed word and included other measures such as increasing the line spacing or "leading", or using shorter paragraphs (a general trend in mainstream writing, particularly in electronic media).
I do agree that CSS is a fairly poor tool for dealing with flexible layout and thus delivering multiple columns without a lot of extra work, however.