An annoying link building strategy used by black hat SEO's alike, but there are ways to combat it.
I use software from a website http://www.akismet.com for all my Word Press Blogs and I would say its reduced the spam I get by 95 percent and any that slips through it learns from its mistakes and I never have problems again.
I do not care if people leave comments on this blog that are worth reading. Even if you leave them for a link back and thats your sole purpose I don't care, but COME ON .... Leave some worth while comments that people would get something from and get a little more creative than leaving the exact same comment on the same blog with an anchor text that is different.
For example - never spam blogs with comments like this:
" I really like your article and I am in the same industry to learn more click here" (and after the click here is an anchor text link - and each comment that is left is the EXACT SAME ONE) DON'T BE STUPID!!!! I will never approve a comment like this.
You have a better chance emailing me saying I want a link (which I don't do) so that should tell you something!! At least those links will be on a higher PR page rather then just a sub-comment on a non PR page... (See the difference??)
This is just a simple reminder to not try to build links by spamming blogs. Make sure and find blogs related to your industry that you like and agree with so you can start leaving comments that are worth reading. I have found that 100% of the comments I have left on blogs (and its been a lot) have been approved. You will have much better success getting links on blogs by following these rules I have laid out.
You will appreciate this post more when/if you ever get into blogging and have to fight off spammers.
Remember I love hearing all kind of comments from people. Even those who do not agree with me. I learn from everyone! I have never professed to know everything, but I just hate dealing with spammers....