The facebookification of the Internet brings with it a stupidification of the content that people produce and share.
The old web was about blog posts (long, though-out pieces of writing) which automatically form links to each other (through trackback) so that a conversation can emerge without the need for a centralized service.
We need to cherish this kind of distributed technology, because it is the way out of the walled gardens. They are the living proof that you can have social without central.
LDA, BTW, is short for Latent Dirichlet Allocation which is a powerful way to classify documents according to the topics they contain.