If you could increase the level of ignorance (worldwide, or in your general location) on a single topic/phenomenon, which topic/phenomenon would you choose?
Math 
handheld technology. I think we’d all be a lot safer if 50% of the people who text and make cellphone calls weren’t capable of it.
[del]Upskirt cameras[/del]
Popular music. I could write some kick ass books about hard rock if other people hadn’t already.
Knowledge about the antics of pop culture personalities would be a good place to start. Imagine a world where no one knew of or cared about Paris Hilton and her ilk.
The concept of smoking. People would be healthier, and land would be freed up to grow food.
Safe RPG handling procedures.
“…bang.”
—Spike Spiegel
The Biblical creation story and timeline! If people didn’t “know” that the Earth is supposed to be 6000 years old, they wouldn’t get huffy about evolution and might be more accepting of science as a whole.
I could get behind this 100%. Bravo!
More seriously, I would’ve suggested nuclear weapons. Far too many people know far too much about them worldwide for humanity’s longterm well-being.
I’d love to make most people ignorant of stereotypes. It’d be fun the next time a person came out with, “All them damn (insert group here) are (insert awful stereotype here)!” most people would just look at em like they were crazy and ask them where they ever heard that.
I’d like to nominate this thread about how to increase ignorance. Let’s just yell at each other.
http://boards.straightdope.com/sdmb/showthread.php?t=515010
Yeah, classy AND smart.
Next, we can start flinging poo at each other.
Religion - ideally, it would be completely forgotten. There’s no rational reason to believe in it, so it would have to be reinvented from scratch, and probably wouldn’t regain it’s former prevalence for a long time if ever. And a religion manufactured in the present would probably be less evil than the ancient ones we have now.