He mentioned he passed (and passed on Secret as well) because he doesn't want to invest in anything that makes it easy for children to be destructive to each other. Let's put it this way, he's not hurting for deal flow and investments.
That seems like flawed reasoning. It'd be better to teach kids to be reasonable human beings irrespective of the medium of communication. If kids want to be destructive to one another, they will be (people can be just as cruel over FB as they can on an anonymous site).
SnapChat's share of voice has fell off the face of the earth, from a branding perspective it is scary. We don't know their user numbers but the buzz has fell flat and the uncool whatsapp just increased their userbase after the facebook deal. I would be scared as an investor if i invested at a billion dollar valuation, since we are not seeing that stable share of voice instagram had. Maybe its a result of bad engineering like Friendster but who knows, they have enough ,money to hire good engineers especially security specialist but their CEO seems to be a bit immature.