Recently I have had to clean up "comment spam" in the Mount Holyoke Alumnae Quarterly blogazine. At first glance it looks harmless enough, but the comments do not add anything to the conversation. Here are some examples:
- This is a great article!
- This is a heartwarming article.
- Thanks, what an inspiring story.
- I really like the different viewpoints.
- These are interesting travel opportunities.
- And so on.
Then there is a web site link to a business offering a product or service for sale, such as running your car on water, travel agencies, or safety videos. This type of spam originally appeared in Internet guestbooks, where spammers repeatedly fill a guestbook with links to their own site and no relevant comment, to increase search engine rankings. If an actual comment is given it is often just "cool page", "nice website", or keywords of the spammed link. This ruined the idea of having a guestbook on many web sites. It was not worth the trouble to maintain.
Given all of the negative connotations of spam, I do not know why a legitimate business would use it to market themselves, which is why many don't, but there are still those that are lured by the low cost and big promises of spam marketing. However, it can easily backfire since many of these web sites and email addresses will be black listed by anti-spam site.
I have a variety of measures in place to prevent spam, but Comment spam is difficult to prevent if human beings are the ones submitting it with benign messages.
If you want to learn more about how to avoid comment or blog spam check out the excellent article on Wikipedia which features numerous links.
Last week I received a new device, the 
