Blog Spam, Cheating and Ethics

I allow anyone to comment on my blog posts. This leads to a nice worldwide conversation, but lately that is being overtaken by about 5-10 spam posts per day, which I have to delete by hand. They are computer generated posts -- I can tell because the same phrases are used over and over again -- with links to e-commerce web sites targeting specific keywords. I have to delete these by hand every day or two. (Fortunately, WordPress is very blackberry friendly, so I can actually delete spam posts from my blackberry from anywhere. But it is slow.)