Metablogging: Tim writes about his optimal target ratio of 70% code and 30% slides in presentations. For a long time I too replaced slides with code until one day Urs and I tried to do presentations with almost no slides at all. Result: mediocre marks. Why? I think that by building a presentation by mostly sticking to code, it gets very tough for people to follow once you loose them. (for either reason - the may be inattentive for a moment or the program being written simply is too alien for them)
My personal optimum now is to divide the topic into many small logic units, each containing one or two explanatory slides (few text and many logical diagrams) and then to do a short and simple demo that anyone can follow (the audience may always contain non-developers) and that proves how the explained sub-topic works, preferably built from scratch or even building on the previous demo.
If a complex demo was to be included in the speech, I would put it in the very end so that subject-savvies may see something new and that people new to the matter don't get shocked if I lost them (after all, it's the end of the presentation).
