You certainly can export a single node - just depends on your expectations. For example, the Indieweb has already done this in a way that I find acceptable. My blog (kickscondor.com) syndicates all the comments to every post (including deeply nested ones.) And it also captures a copy of all posts that I respond to (all the way up the chain going backwards.) This is sufficient for me. No need to export anything - it's already there in my own storage. You could also say that you'd need a snapshot of the entire Internet to provide context - but that's Just unreasonable.

I think the a Web itself already has had a 'network effect' larger than that of Facebook or any individual subnetwork.