Even speeches that don't overload on information can be accused of having too much—if that information isn't interpreted in an interesting way. Granted, it's a lot easier to give information than to look for ways to make it interesting and useful. (But no one said giving a speech was easy.)
The major fault in technical presentations is relying on the hard-core technical data to carry the day, and having too much of it. Everyone—scientists included—wants a presentation that doesn't throw findings at him but interprets facts and weaves a story. Almost all of the technical presentations I have seen needed their information reduced by half and their visual aids simplified.
Humanize and personalize your data. After my son took a college course on military history, I asked him what struck him as the most interesting thing he had learned. He said he was amazed by how long it took soldiers to load the early guns and how difficult they were to fire. He saw the data presented to him in terms of human consequences. Let your audiences do the same by presenting your facts in a human context.
It's also very easy to make false assumptions about the level of data appropriate for your audience. For example, in talks to upper management, speakers feel they can fill speeches with technical information, because the audience is at such a high level. In fact, by the time people get to upper management, the skills they wield are generalists' skills; they are no longer as knowledgeable of the technical details as the technicians below them.