Chinese comment spam robots resulted in my (low brow) site host shutting me down. While I saw thousands of attempts at my login, there were 65,000 attempts to post comments on one of my (old) posts. Seems the robots love me!
I'd point you to the article on my page regarding which subnets (all Chinese) I ended up blocking, but I think that such links are frowned upon. If you search for "Chinese Comment Spam robots" in Google you should find it.
On a related note, I wonder how WordFence and Bulletproof are head to head. Bullet proof adds a ton or rules to htaccess. Eventutally I gotta think that will end up with more overhead than processing the PHP itself.