It's a fact, if you have a Wordpress blog with open comments, then you will get spam postings. Almost 90% of comments on blogs are spammers. Sad but true. People often add comments to blogs just to get back links and visitors to their own blogs. They may not have any interest at all in your post. Some of these commenters will try to camouflage this while others blatantly comment away without a care in the world.