Back in the mid-1990’s when I was working on the MSN Engineering team at Microsoft, one of the projects we started to work on was a tool that would allow people to post comments about web pages "on" the webpage. That is, it was a feature in Internet Explorer very similar to the "Comment" feature in Microsoft Word. As with far too many Microsoft products, they started it, then shelved it.
I was really excited about it back then because of the great potential for true customer service feedback about companies (think direct "Better Business Bureau" comments) as well as support for products, and relevant information for daily updated websites. It also included an "inline" feature, that would allow you to highlight a word/sentence/portion of the webpage and comment just on that, rather than the whole page. Tremendous possibilities for those who might care to use it.
Fast forward from 1996 to 2009 (~13 YEARS?!) and Google introduces a feature in their Google Toolbar called "Sidewiki". Yes – 13 years. Virtually the SAME feature – comment on any webpage, or on just a piece of text on the page. Although the Microsoft version I started testing in ’96 had the comments at the bottom of the page. So the question is, where is Microsoft’s innovation? Or, where is Microsoft’s follow-through? sure, it’s an insignificant feature that probably 90% of current web users won’t see or understand, but who knows… If Google makes it a default part of their Chrome web browser, or it just catches on like Facebook or iPods, it could be a "can’t live without" feature of the web.
In any case, install the Google Toolbar and check it out. Be sure to enable the feature in the toolbar settings, then go to your favorite websites and see what others have written about each page of the website, or about specific parts of a page… And better yet, before you buy from a company, go see what others have to say about them in the Sidewiki – you might learn something new.