http://akihitok.typepad.jp/blog/2006/02/ngram_fcd1.html
as the author above mentioned, spoken-word-form of writing is quite common in blog. i think that is the biggest reason they applies it.
also suggestive idea the author says that we can use several blog-search sites(technorati etc.) in accordance with intended use.
in addition, N-gram is applied on the system i've been working on so far on buisiness. now i finally recognize why it tend to find the contents on blog more easily than those out of blogs....
