Oh for the days when spam was spam and your blog tool deleted it for you! Not so much, anymore. Spammers have evolved – they are as likely to be real people, as robots. When they are real people, they tend to bypass your spam-tools because they write intelligent sentences (well, intelligent to a 'robot' or software tool…not so much to a real person).
These days, in the four blogs I write in, spam is prevalent to a high degree. If I do not check these blogs on a daily basis, the spammers have a field day adding inappropriate or just off-topic content, often overpowering the real comments. A lot of spam seems to come from Ugg boots – although, I'm pretty sure the company is not sending that spam. It's a popular term – hence, the spammers use it to try and fool people into thinking it's legitimate content, and fool the spam tools by using a legititmate word/phrase.
Here's the skinny – spam is anything that doesn't belong on your blog. Spam comments often come with links to porn sites, sites that have no relation to your blog topic, or links to places looking to generate traffic on your 'dime', so to speak.
These can include places that are relevant to your blog and blog topic – such as pet focused businesses.
In that case, you need to determine if you want to send traffic to that business/blogger. I often allow those comments if they are short and not blatantly promotional. So, if a person hoping my women's business blog will send them traffic writes a short comment, "This post really hit home with me," which means nothing and could be applied to ANY blog post, and also includes a link, I might let it go the first time. If that person continues to share the same kind of comment, over and over… well, that's real spam and I delete those comments by sharing them with my blog platform as "spam".
Sometimes, you see a comment with misspellings or bad grammar. In that case, I try to visit the link the commenter provided to see if they're legitimate (have a real blog or website) to determine if the comment is poorly written because their first language is not English. Then, I make my choice on what to do based on that result. It's a good practice to err on the side of compasion and giving the benefit of the doubt. I have actually fixed comments, when I know the person and recognize that she/he probably had "fast fingers" (typed without realizing the errors made). If there is no link to research the commenter, well, I probably delete it. It just depends.
Spam is not likely to go away any time soon. According to Wikipedia, "Spamming remains economically viable because advertisers have no operating costs beyond the management of their mailing lists, and it is difficult to hold senders accountable for their mass mailings."
Here are a few more links exploring the issue of spam and how to deal with it:
Tell us how YOU deal with spam on your blog.