Most of the bloggers I know are been spammed, there are quite a few different ways to stop spam from occurring on your site.
One would be the use of a Captcha plugin to display an image with some text the commenter has to input into a verification field. While this is effective, it can annoy visitors and you will ultimately loose comments on your blog
Another way, is to use the Askimet plugin that is packaged within WordPress. Once you have it installed and running it will catch spam comments, as well as a script can. Personally the script hasn’t failed me once, it has never held back a legit comment and has never missed a spam comment.
Now this is a great way to keep spam ‘Unapproved’. But I go one further and ban the spammers IP’s from the blog. I have banned 4 IP’s so far and I haven’t had a spam comment in 5 days, before I was getting one every few hours. To ban the IP’s from viewing my blog I use the WP-Ban plugin. Askimet provides the IP’s, then if an IP spams more than twice it I add it to the banlist.
Just a quick little tip I thought i’d share.