After thinking about it for a while, there is also another aspect about multipass lighting I always feared, and its really trivial to handle, just like fog.
Transparent objects are rendered the same way as fogged objects: the final shaded pixel is linearly interpolated with a color, just like fog, but this time the color comes from the destination pixel. If you do the math,or if you take a look at my previews post, it becomes clear that transparent objects can easily be multiopass lit. Both techniques can also be combined as well.
Coder's Diary 