You will end up on my bad list if you just put index pages in those directories... you need to put ALL your html inside each directory, so that you have complete sites. If the folder changes (either up or down) I tend to decline the site because you have doorwayed me and put me in a place where few surfers will ever see my link... when you create full folder sites, there is way more chance that SE bots will actually see this as a distinct site and actually pick it up.
http://www.porn-free-site.com/xxx/ti...ter_muffins/b/
goes down a level from there... no reason for a bots to index it, so no reason for the bot to give my link back any value.
Alex