Link popularity has been the main technique for search engine marketers for at least the last few years. Some marketers have become so obsessed with link popularity that they have resorted to automated techniques to help them acquire one-way links. Some examples of link spam methods that are still being exploited are:

Guestbooks - In a woebegone era people placed simple scripts on their websites, with the hopes of getting feedback from their visitors. A great number of these scripts are still in existence. A web spammer will identify a guestbook because of its' footprint. Millions of these guestbooks have been abandoned and are not monitored by their owners. For this reason, automated guestbook spamming has been rampant. An interesting thing about Guestbook spam: some of them can even be spammed too death. Since many of these are old CGI scripts, they can't handle the volume of spam messages, and end up crashing. At that point the Guestbook will live on until the domain owner removes it.

Blogs - blogs became even more popular than guestbooks. they've been installed by the millions and abandoned at 90% rate. Blog software prior to 2005 had a default setting which allowed comments to be published without prior approval. It also allowed live html, so these blogs are out there still begging to be spammed and many are each day. What ends up happening is they get so many outgoing links that the page becomes a massive size, and at some point the page may even have trouble loading.

Forums - a frequent victim of webspam. Since almost all forums allow users to submit material without pre-moderation, web-spammers will attempt to post to them. The good news about Forums is that are usually not abandoned like Blogs or Guestbooks, and usually someone will come along and clean up the mess. This isn't always true, but it does happen quite a bit.

Any form on the internet that allows html is vulnerable to webspam attack. Without some sort of moderation it's impossible to ensure that malevolent html will not be inserted. if you don't pre-moderate the form, make sure you receive email notifications whenever the form is submitted. If you don't at least check the form often, it's inevitable that you'll be spammed by one of the numerous bots on spam duty.

Search engines introduced the rel nofollow tag in order to deal with the rising tide of link spam. All popular blog software comes with the nofollow in place, so the main risk of Webspam is to legacy blogs installed prior to 2005. Nofollow essentially tells the search engine that the link is untrusted. In essence it says this link was entered by a person other than the website owner, so treat it with a grain of salt. Forum software makers have also been quick to add nofollow to their core technology. The fact of the introduction of nofollow gives great insight into how much trouble search engines were having with the enormous load of link spam. Basically they threw their hands up and admitted defeat. Nofollow has had an enormous impact on Webspam, but there are still an awful lot of blogs and forums out there that haven't been patched.

Link spam appeals to certain web marketers for obvious reasons. It's a scalable and free solution to building link popularity. Web marketers who automate the process can quickly vary their anchor text between 'runs'. This will give them a wide variety of links from a broad spectrum of websites located on diverse IP addresses. This is normally a sure-fire recipe for success for virtually any website. By simulating the link popularity of a popular website, the link spammer is able to fool the search engines into assigning it higher rankings. The manipulation of link popularity has become a major issue to all of the search engines. Each will offer more and more attempts at reducing this threat, but unless search engine rankings are based only on on-page variables, it will always exist.