I was thinking about slides for conferences. (I tested with the word "banana" anyway.) In conferences, walls of text is a very common design error.

I teach math in the first year of the university. When I started, One very useful recomendation was:

> Whater you write in the blackboard, they will copy in their paper notebook and may read and learn some day later.

> Whaterver you only say, goes away with the wind.

So I try to write down in the blackboard everithing I say.

So slides for a classroom shoud have more text than what I usually expect.