The history of science is replete with discoveries that were considered socially, morally, or emotionally dangerous in their time; the Copernican and Darwinian revolutions are the most obvious. What is your dangerous idea? An idea you think about (not necessarily one you originated) that is dangerous not because it is assumed to be false, but because it might be true?
Respondents include many whose work has appeared on Boing Boing before, including: J. Craig Venter, Sherry Turkle, Danny Hillis, Jaron Lanier, Rodney Brooks, David Gelernter, Kevin Kelly, Freeman Dyson, George Dyson, Rudy Rucker, Mihalyi Csikszentmihalyi, Clay Shirky, Ray Kurzweil, and Clifford Pickover.
# A 24-hour period of absolute solitude
Our brains are constantly subjected to the demands of multi-tasking and a seemingly endless cacophony of information from diverse sources. Cell phones, emails, computers, and cable television are omnipresent, not to mention such archaic venues as books, newspapers and magazines.
This induces an unrelenting barrage of neuronal activity that in turn produces long-lasting structural modification in virtually all compartments of the nervous system. A fledging industry touts the virtues of exercising your brain for self-improvement. Programs are offered for how to make virtually any region of your neocortex a more efficient processor. Parents are urged to begin such regimes in preschool children and adults are told to take advantage of their brain's plastic properties for professional advancement. The evidence documenting the veracity for such claims is still outstanding, but one thing is clear. Even if brain exercise does work, the subsequent waves of neuronal activities stemming from simply living a modern lifestyle are likely to eradicate the presumed hard-earned benefits of brain exercise.
My dangerous idea is that what's needed to attain optimal brain performance — with or without prior brain exercise — is a 24-hour period of absolute solitude. By absolute solitude I mean no verbal interactions of any kind (written or spoken, live or recorded) with another human being. I would venture that a significantly higher proportion of people reading these words have tried skydiving than experienced one day of absolute solitude.
Link  to complete list of respondents, and their answers.