Akismet has blocked no spam comments from facebook to my blog by Wordbooker plug-in.
But I couldn't solve the problem. This is because I couldn't found Manage -> Akismet spam page.
Akismet thought my friend's comment was spam!
This is also called a "false positive," and is a comment that is not actually spam, but is mistakenly marked as so, since computers aren't perfect. That's okay, it's easy to unmark it and let it back into the stream of legitimate comments.
Go into your administration panel, and to the Manage > Akismet Spam page. Find the comment, and click on the Not Spam button, and the comment is spam no longer.
Where is the Akismet Spam page?
I have used wordpress ver 3.0.1