Or maybe our algorithms just aren't good enough. Suppose you use bayesian filtering on the text surrounding the links to determine whether the connection is good or bad. With a reasonable amount of data it should be possible. Note: I'm not an algorithms guy, I do business and strategy and a wee bit of programming, so maybe the example isn't good, but I thinkthe point is.
Google already analyzes backlinks in their context to determine how relevant the anchor text is to the topic of the page. Determining sentiment (the topic of the NYT piece) is considerably harder though, because it would allow for spammers to write negative articles about a site and link to it and negatively affect its rankings. Also, determining the tone/emotions of a piece of text is probably one of the hardest thi…
As for determining sentiment, it's not something I've ever tried to do, but is it really that hard ? Intuitively I would think positive and negative articles would have significantly different distributions of certain words.