So I've kind of come full circle and think I'm OK with "Statistical" and "Log-Based" subcategories, as long as we don't try to shoe-horn every method into one of the two (and maybe make the descriptions clearer / more correct). I'm still unsure about "Simple" vs "Advanced" - maybe "Simple" vs "Learning". I think what I'd really like is a category of all targeting strategies, too, like we have with Bots. Is it bad practice to be doing this (pages in category and a subcategory) all over the place, or does anyone really care? Any other input?