The second you dim the lights and go into "presentation mode" is the moment you move from a two-way conversation to a one-way lecture/broadcast. It's hard to be interactive when you're behind your laptop, at a podium, watching your slides on the small screen.
Then there's the phenomenon of "talking to the slides", where the speaker is constrained into following a script. Although some can do it, most presenters (including me) aren't capable of dynamically reconfiguring their slides to customize in realtime for a particular audience. So the speaker just forges on, slide after slide, saying what's already ON the slide, regardless of what he learned about the group. Then again, asking the attendees for feedback is dangerous when you're following a script, since it's tough to really incorporate anything they say.
But given how many people hate slide presentations, why is it universally assumed that where there is "a talk", there's PowerPoint (or its much cooler cousin, Apple's KeyNote)? Conference coordinators rarely ask speakers if they'll be projecting slides. They send out the slide templates, then start demanding your slides several weeks before the show. Saying you don't have slides is like saying you'll give your talk naked. "You mean... you're going out there with nothing???"
I know the arguments in favor of slides:
Visuals are more memorable than words alone.
True. There's almost nobody in the computer book business that believes that as much as we do. But bullet points are still the prevailing content of most slides, and they usually add nothing unless the speaker truly sucks, or has such a dramatically hard-to-parse accent that it's the only way you can get the info.
You have no choice when you're presenting something that must be shown.
There are times when the very content you're speaking on directly relates to something you need or want to show. A screen shot, a design, a building, an animation, etc. Often you need to show quantitative data in a chart or graph. These are completely valid reasons, and slides might indeed be the best way.
Read on to this great article, it's worth a full read.
But they aren't the only way to show that data.
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