Word verification on comments

Yes, I am very sorry to say that I have had to implement word verification on comments now. I have been bombarded with spam comments for a long time now. It was always a nuisance to be reading about printer ink cartridge sites and requests to link to the information on my site (though I never figured out why anyone would send a spam comment like that). But now I am getting really insidious spam comments for adult sites and I'm really trying to combat that. The suggestions on Blogger's help site say that by adding word verification the spammers will eventually give up if they can't get through. Obviously moderating the comments is not enough so I'm giving the verification a shot. I know how irritating it is to have to type in letters and numbers every time you leave a comment but I hope if the spammers give up then I can stop using word verification too.