I know; I was surprise too. But to be honest, when I googled it, I even didn't know what to type in Japanese if I want to type "forum".
That's how less I don't know? Or, that's how less common the forums are among Japanese...?
When I wrote "blog", I meant more personal bloggings, not social networks.
It of course could be, like facebook and/or Twitter, but there's "ameba" blog (ameblo), for example. I believe people prefer writing blogs and talk about any topic with people who come and visit their blogs.
If you write "アニメ ブログ" to google, you'll find quite a many lists of blogs about anime/manga.