I was watching my brother mess about in Flash a few days ago, and was wondering what he was doing. He was making a trail of dominos fall over, in frame by frame. I told him that doing it that way was a needless waste of memory and time, where a tweened and eased movement would create exactly the same effect.
You must all remember, of course, that when Flash was first created no one thought that it would become a huge animation package. As someone said up the thread, none of the techniques should be discounted. Frame by frame is excellent for motion, but most frame by framers end up with low detailed limbs and motion (no one's going to make 24 perfect images for a single second of animation), whereas Tweenimation (gratz to the person who made THAT up) is perfect for detail (due to not needing to redraw the thing), but is not the best thing in the world for range of movement without a few hundred extra symbols and some tender loving care.
And for all those who don't like tweened motion at all, one word. Xombie