Delete all marked as SPAM

I think the time has come to actually start to delete blogs that I have been marking as spam on my blogs.

I had been marking them as spam only, so that if a user was to get caught up in it, who complained, I could restore their blog.

However, the blogs that I have been marking as spam for the past few months has not complained or anything.

So to now free up some space on the database etc, what would be the best way to delete the users & sites who has been marked as spam?

Is there a way that this can be done?