It works, but blog spamming is pretty lame. If you're going to use it as part of your strategy then make sure you add some value to the blog.
I have a couple of blogs myself, they are not that great, but I laugh at the blog spammers. I get junk submitted all day long. I get very long article like comments, almost like sale pitches, to article type comments where every other word is some type of anchor link, viagra comments, software comments, and I also get the milder type comments, "your blog is so great, very interesting, hope you add more content" thats total BS, my blog is not great, and its not very interesting at all. Every comment I get on my blog is self serving one way or another, so when I read comments like "I just love your blog" I know they probably have not even looked at the blog much at all, they are there just to get some self serving link within the blog, and thats it. not once have I had any person add anything that would provide any actual value to the blog.
Blog commenting does still work but spamming blogs with your links is not a good idea. Like the others in this thread explained, make sure you comment has value and is relevant to the article/post.
now most of the bloggin platform provide anti spam policyto protect the blog from these kind of cmments so you need to check for no follow or do follow ..