This is related to my Technique and Principle thread.
The concept of "form" is that when attacked a certain way, you react in a predetermined way. This counter can come from forms, partner drills, etc. You practice this move over and over with partners so that when you encounter this certain attack, you will be prepared.
The concept of "no-form" is that you learn the moves, you make them a part of you, and you forget them. But since the elements are still present and - at this point - instinctive, when you are attacked, you will respond with the same principles though they may manifest themselves differently than before. Think of Legos; you have two castle sets and you start by building them individually. After you understand how the Legos go together and what makes a good Lego castle, you start mixing/matching pieces and features to make whatever kind of castle suits your purposes and without instructions. But you have to build a lot of Lego castles before you learn how to do this.
And what method do you use to train for self-defense? Are you an advocate of form or no-form? What method is best for a novice/intermediate/advanced student? Is there a best method? What role do the training methods of sparring/partner drills and prearranged sets play, if any, in your fighting?
The primary goal of this topic is to get people (including myself) thinking and discussing. If you think something is good or bad, state your reasoning. I imagine we will here a few "forms are useless" comments (among others) here and I think we could all benefit by picking each other's minds.