Well I disagree with justice Kagan. I think the Court gets the gist of what Facebook, etc, is, and I don't think there is much that is valuable about having really deep understanding of the technology.
I think technologists confuse technology with ideology. Facebook is a technology that lets your friends see messages and photos you post, like a private bulletin board. I think every Justice gets that. All the other stuff, about what sort of social role that technology should play, that's ideology and politics.
As an aside, when younger people say older people don't get technology, I think its usually a proxy for social disagreements. E.g. My mom (62) has a Facebook, and iPhone, iPad, etc. She gets how it all works. She just doesn't approve of people posting pictures of themselves in revealing outfits or airing personal business in public on Facebook, or teenagers sexting pictures on their iPhones. That's not her not understanding technology. That's her having different social views.