Google (Nasdaq: GOOG) More about Google on Wednesday launched Sidewiki, a Web annotation tool that serves as a comment forum for Web pages.

Sidewiki ranks entries according to their relevance, as determined by Google's own algorithm. It will also place those comments on Web pages that carry the information which sparked the comments.
About Sidewiki

Google Sidewiki appears as a browser sidebar. It is being released as a feature of the Google Toolbar for Firefox and Internet Explorer, and it will also be available in Chrome and other browsers.

The first version of the Sidewiki API (application programming interface) is available now. It lets users work freely with the content created in Sidewiki, Sundar Pichai and Michal Cierniak said in the Google Blog post announcing the annotation feature.

Sidewiki is part of Google's larger vision, which is to gather metadata about what conversations are happening and what trends are occurring out there on the Web, Carl Howe, director of anywhere research at the Yankee Group, told TechNewsWorld. "The whole idea of being able to annotate the Web has been around for a while and, while lots of companies have worked on it, only Google probably has enough critical mass to make it happen."

Sidewiki lets readers of a Web page post comments on the side of the page; pushes the comments out to all Web pages that carry the text which sparked the comments; and pulls in relevant posts from blogs and other sources that talk about the page.

Comments are ranked according to how Google's Pregel algorithm defines relevance. "We worked hard from the beginning to ensure that users will only see high quality, useful and relevant entries in Google Sidewiki," company spokesperson Eitan Bencuya said.

The algorithm incorporates various signals about the entries to rank them in terms of usefulness, Bencuya told TechNewsWorld. These signals include language modeling for the text and information Google has about the author, such as the quality of his or her previous Sidewiki entries.

Whether those signals would be an accurate indicator of the relevance of a comment remains to be seen. Just because someone makes a pertinent comment on one topic doesn't mean his or her comments will be as relevant on another topic.
Ownership and Other Issues

Web page owners who install Sidewiki may not face a free-for-all, as the application provides for some management of entries. "We enable the community to monitor Sidewiki entries by voting up content that is useful and informative and voting down irrelevant or unhelpful posts," Bencuya explained.

The community can also flag any illegal or copyrighted content by using the "Report Abuse" button.

Site owners who want to claim ownership must have claimed their site in Google Webmaster Tools first, Bencuya said. This lets them post a special entry that will appear above all other entries in the Sidewiki sidebar to introduce users to their page, and lets them respond to comments.
Getting Started With Sidewiki

Adding Sidewiki to your page is easy -- just download the latest version of Google Toolbar and enable the Sidewiki button in the Toolbar Options menu. To enable or disable Sidewiki, click the Toolbar's wrench icon, select or deselect the Sidewiki checkbox on the Tools tab, and save.

After enabling Sidewiki, click the button to open the sidebar. This lets you see Sidewiki comments from other people about information in the pages you are on. It also lets you write your comments.

To share a Sidewiki entry with a friend, click the "Share" tab at the bottom of the entry or post it to your Facebook More about Facebook or Twitter More about Twitter account.
Problems With Sidewiki

Sidewiki has already generated skepticism and fears that Google is trying to own the Web and monetize it to its own benefit. For example, writing in his Daily Telegraph blog, Andrew Keen called it a brazen attempt to own the Internet. By replacing the Web page owner's comments section with Sidewiki, all comments on the Internet would, in theory, be owned by Google, which would sell ads around them, he contends.

Not so, Google's Bencuya said. "As we explain in our terms of service, you retain copyright and any other rights you already hold in content which you submit, post or display on or through the services," he said. "Additionally, we have no plans to monetize Google Sidewiki at this time," he explained.

"Sidewiki appears to give Google ownership of comments, but it also potentially improves the usefulness of those comments," Rob Enderle, principal analyst at the Enderle Group, told TechNewsWorld. "That may be a strong enough offsetting benefit for the loss of control by Web page owners."

Enderle expects Google to eventually own the ads around comments on Sidewiki. However, it should move carefully, Enderle said. "It would be wise for them to share the related revenue, and I'd expect it to do that," he explained.

"Ultimately, Google may provide revenue-sharing as part of a comprehensive package to the site owner for advertising revenue and related services," he added.

没记错的话，以前（大约2000年）的腾讯浏览器也有类似功能。不过当时的腾讯并未像如今的Google达到critical mass，因此该功能没能吸引多少人气，从而也无法形成positive network effect。