For Pros and Cons reviews, the aspects are identified as the frequent noun terms in the reviews, since the aspects are usually noun or noun phrases (Liu, 2009), and it has been shown that simply extracting the frequent noun terms from the Pros and Cons reviews can get high accurate aspect terms (Liu el al., 2005).
more than $156 million online product retail sales have been done in the US market during 2009 (Forrester Research, 2009).