In a TED talk, Dimitar Sasselov, a co-investigator on the Kepler mission, said their current best guess for the number of Earth-ish, habitable, planets in the g

In a TED talk, Dimitar Sasselov, a co-investigator on the Kepler mission, said their current best guess for the number of Earth-ish, habitable, planets in the galaxy is looking to be like 100 million (at about the t=9:20 mark in the talk). That is, naturally, an early guess from extrapolations and such, but still it is more based on something than the based-on-nothing and intuition guesses that sometimes float around in these discussions.