Finding the right balance is really a difficult question. It is true that I have a tendency to fill slides with a lot of material, in order to exploit complementary channels : while my voice gives the general idea, or emphasizes a particular point, the slide can convey more detailed information, and people in the audience can grab more content if they are especially interested in one particular aspect.
Probably I like this style because it corresponds to my own way of learning. When I was at school, at a time where beamers were rare and expensive, most teachers used physical transparencies. Some of them had the habit of putting the transparency and immediately hiding it with a piece of paper; then they would progressively uncover the slide, one point at a time. I hated that habit, because I was forced to think at the same speed as the teacher. If I see the global picture at once, I can immediately choose which points seem more important to me, and focus on them, maybe already preparing a question, or think back at what was said before, or anticipate what is probably going to be said next. But if the teacher dictates the rhythm, and decides to pause for 5 minutes on a point which is important to him, but not to me, or decides to quickly skip over a detail which I need to elaborate in my head, then I'm in trouble.
The modern way of uncovering slides one point at a time is the Takahashi style (lots of slides, very few words, huge font), which seems much praised in the Perl community. I must admit that I was quite impressed the first time I saw a presentation in this style : it is quite efficient for a lightning talk, or to create some suspense at a particular point in a presentation. However, if many speakers adopt this style just out of fashion, without deliberate thinking about which effect they want to achieve, then at the end of the day it becomes quite boring, and I feel like having watched several hours of videoclips. After such a day I don't really remember what were the highlights.
