They aren't humans. They're spam robots that troll through the web for "live" blogs to post their messages on. It's a program, and while Blogger was remarkably free of them for a long time, that's no longer the case. I've been seeing spam on a lot of Blogger blogs in the past couple of weeks.

It's because of comment spammers that I close old blog posts to comments. The bots that attack Movable Type start searching in old archival posts first and work their way forward. At one point, I was getting upwards of 17 comment spams a day before I found out how to stop it. I only get one or two comment spams every couple of months now. Don't know if it will help you on Blogger, but thought I'd mention it.
 

Bridge, I just checked Blogger out and if you go to your Dashboard and look under Comments, you'll find a setting which says "Show word verification for comments?" If you click "yes" this should take care of your problem. It will prompt commenters to enter the code they will be shown into a space provided in order for a comment to post. As only humans can do this, the spam bots are thwarted and move elsewhere.
 

Thanks Aravis! For this helpful hint and for your continued support.

pbw
 

You're welcome, Bridge. Hope it helps. :0)