I feel like you missed listing a big change: with the rise of UGC sites, the boosting of results of anything on an "important" domain doesn't seem valid anymore

I feel like you missed listing a big change: with the rise of UGC sites, the boosting of results of anything on an "important" domain doesn't seem valid anymore. Just because something is on twitter.com doesn't mean it's highly relevant, since anyone could've posted it. But it's fairly easy to google bomb someone's name by just registering a Twitter account and listing their name as owning it. Similarly, stackoverflow.com doesn't have very good answers for a number of technical topics, but it's often on the first 10 hits, even when the answers are useless and there's much better answers ranked lower (like project mailing list archives).