Weblog SPAM

I noticed several weblog spam here. What does it mean? After sending new weblog post a received mail notification, that some new comments was added to my weblog. Of course I was curious and I clicked on link. There was usually comment like: 'Your weblog is so cool ... link at my weblog' ... and there was some advertisement. To prevent from this you will have to type some word verification, when you will want to leave me any comment. I hope, that it will not bother you and I hope that I will not have to do some other restrictions in the future.