Each year Google, Nature and O'Reilly Media invite some of the sharpest thinkers to Science Foo Camp in California. At the 2010 gathering, we asked a skeptic, an internet guru, a philosopher and some scientists about their worries for the future. Speakers in this four-part video series include astrobiologist Paul Davies, climate scientist Michael Mann, broadcaster Andrea Marr and computational biologist Adrien Treuille.