junk mail on blogs?

I've always found it very ironic when people in advertising complain about unsolicited mail, advice, sales and the like, but this is a new one for me. I have stated to receive junk mail on my blog in terms of linked false comments (as much as I would like to believe they are true). Does anyone know the origin of this kind of advertising?

Here are some of the comments I've received (strangely enough after posting an article about how advertising prevents smoking in teens):

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I'm waching blogs all day long and I found yours which is really nice :)cialis

Thanks, you really have some interesting stuff on your site. keep at it.phentermine

Okay, I've figured it out - the word verification option - as you can see below, some more annoying posts after I got rid of the other.