Every web 2.0 builder is most likely exposed to comment spam because of the social nature of this generation’s web applications. This requires considerable effort in building a system that is not easily gamed by spammers, to avoid it being rendered useless by nonsense content.

Aside from email, comment spam is the next most prevalent form of spamming. This is largely because of the nature how google ranks pages through its PageRank algorithm.

Automattic’s Akismet has been one good weapon against comment spam since its inception as WordPress’s spam blocking mechanism. Thanks to its useful API, you can now use Akismet to check your comments against their spam–fighting magic from any PHP4–based system, using this PHP class from Pablotron.org.