I agree that 'poisoning the meme' is a real danger, and that SIAI has historically had both positives and negatives with respect to its reputational effects. My net expectation for it at the moment is positive, but I'll be interested to hear your analysis when it's ready. [Edit: apparently the analysis was about asteroids, not reputation.]

Here's the Fidelity Charitable Gift Fund for Americans. I'm skeptical about asteroid in light of recent investments in that area and technology curve, although there is potential for demonstration effects (good and bad) with respect to more likely risks.