Most spam comments are easily identifiable because they usually have little or nothing to do with the post and they usually end with a "hey why don't you visit my site at ..." or slightly more subtly they do make a comment on the blog which can seem genuine and then just leave their web address as their email.
Now before Google Penguin (not to be confused with the Cranky Penguin) I suspect these spam posts were put there by SEO companies who knew that google rewarded websites that have one way referrals to their websites ... so before the Penguin you paid the SEO company to increase your website ranking and they did this by (among other things) putting spam comments on blog sites which had some relevance to the business and which therefore increased that businesses google ranking.
The internet is such a brilliant place.
Except now Google Penguin has turned this on its head ... as now websites are penalised for having too many links from "link farms".
Who could think that's confusing.
So today I got an email from what sounded like a SEO company representing another company called cleaning for a reason dot com dot au demanding that I remove the link I have to their website as it may affect their website rankings with google. Furthermore, they threatened that if I didn't do so they would put a "disavow link" on my site.
Somewhat confused as to why I would ever link to a cleaning website, I checked out the webpage and sure enough ... there was one of those clever little spam comments at the bottom of the blog linking back to their site.
So, I removed the comment ... which was probably put there by the same SEO company that's now asking me to remove it.
God I love the internet, I love the Google Penguin and I love the Google Panda.
I just can't wait for Google Godzilla ...