I don't mind reading long texts online. What I do mind is the terrible control of line height (leading) that most sites seem to have (this one included!). If you are creating a web site with content of more than one sentence would you please manage the line height as well as you manage the font size. The default line height for most browsers is too small. For example, in this image the text on the left uses a 14px font with the default line height while the text on the right uses a 14px font with an 18px line height. I find the text on the right much easier to read than that on the left. (Click the image for the full sized example.)
Update: I fixed this blog's line height. I doubt that this will enhance the value of the content, just make its worthlessness so much more obvious!