As I troll through the code at times trying to polish here and there I notice small issues to bring up --
Line separators. Lots of code independently reads System.getProperty("line.separator") in order to output a platform specific line break. I argue this is actually slightly bad, since it means the input/output formats of Mahout aren't fixed at all, but can vary by platform. Output on Windows isn't read properly by Unix, etc., perhaps. It'd be simpler and more compatible to use '\n' always. Thoughts? (And, recall we don't really support Windows so well anyway, which is the odd man out in this regard.)