The wrapper matters
When you have a big idea, the question is, how to spread it?
You can go through a traditional publisher and have it printed in the tried and true way, like Clay Shirky. I had a chance to read Clay's new book a few months ago. No surprise: it's pure gold, unalloyed insight about the state of media and the world.
If you're looking for big ideas and are prepared to lose a little sleep, there's no better book to buy right now.
You can have someone take a short speech based on your book and have them turn it into a animated video. Dan Pink's video has been seen about 20 times as often as his book has been purchased. Video spreads.
You can turn your idea (like a focus on entrepreneurs) into cool trading cards, like Evan did.
You can skip the printing altogether and start your own video university, like Khan Academy.
Perhaps write a short manifesto and watch it spread as a free ebook. Like Changethis, a free service that has reached millions with the work of top authors from around the world.
Don't forget podcasts or mp3s, which can be very funny or motivational.
Consider starting a conference with a unique platform and worldwide reach, like TED.
Or you can blog your idea for several years in a row, slowly building up trust and making an impact over time.
Of course, there's no right answer. But there's probably a best answer that matches your time frame, budget, audience and idea.