Unwanted comments

I was very surprised two days ago when I was notified that someone left comment on one of the post on math pages.. This at itself is a rare things to happen, but this is not what surprised me. The comment contained only three words and two links to some site. Classical spam. Since visiting on this site will almost surely result in getting a virus or a spyware program I am not putting a link to it. I deleted the comment of course, and turned on comment moderation - just in case. I thought that the story will end, but it didn't.

Yesterday I received another such comment. Slightly different words, but still two links to the same site. I just deleted it. I was sure that this will be the end to the story... Today I got another one. Deleted it and reported the one who left it - he was using a blogger account. Hope this will end the story...

I am surprised why I am getting this spam at all.. My blog is relatively new and has a low page rank. I see no reason for spammers to waste their time putting links here..

Update 2.3.08
I am still getting these comments... I really don't understand why. The person who leaves them uses blogger accounts, so the only result is that I report him as spammer. Well it is his choice..
The last comment was slightly longer than the previous - a whole 10 words - with a very obvious link to the same site.