Earlier today Google announced the release of Sidewiki, a universal web page commenting system that allows anyone with the Google Toolbar to add comments and feedback on any web page. The web is abuzz with the news. The video included below gives a good overview of how Sidewiki works.
If you run a website, like many of our readers, and you have an account system, you probably have problems with spam. One of the main sources of spam is users who register using disposable e-mail addresses. These can be generated by spammers programatically, using services like the Guerilla Mail API I covered previously, and used to make tons of accounts to try to get blog spam through. If this is a problem for you, the DEA Filter API can help.