In a breezy article on sentiment analysis, Alex Wright quotes Bo Pang saying:
We are dealing with sentiment that can be expressed in subtle ways.This is so true with the examples I've encountered while working and my favorite is this one I saw on iTunes recently.
While I commend Alex for writing an informative yet accessible article on the topic, I disagree with the article's opinion that sentiment analysis is a series of "filters". That is clearly an euphemism. Any working sentiment analysis system is actually an engineering feat often consisting of a series of hacks duct-taped by a glue handling special cases.
The article also seems to suggest that extracting factual information is somehow easier than opinions. I invite them to participate here.