It might also depend on the length of your chapter. The guy who stopped at 8 chapters may actually have less up there than the guy who stopped at 3. My opinion is that the first uploaded chapter (not necessarily the first chapter of the book) is the most important: it’s the one visitors see first, and I suspect that a lot of people make their decisions based on that chapter alone, without looking at the rest. Anything else after that is supplementary: in case someone wants/needs to browse some more before being convinced.
It might be worthwhile to consider what @Kyle James did with his uploads for "Not Afraid of the Fall": instead of uploading full chapters, he uploaded a lot of very short excerpts taken from various points in the book; a few are only a paragraph or two. On the plus side, he gets to pick and choose the tastiest morsels of his text; everything is bite-sized and feels like nothing, so the reader has no problem eating them up like potato chips; and it gives a broad overview of a lot of different places in the novel. On the minus side, seeing a long list of "chapters" is a bit daunting, and might discourage people from looking at all, if they think each is going to be a full-length chapter.
