Google Sidewiki isn't a new concept, it's something that many have tried before. The concept is that you could be visiting a webpage and then you feel you've got something to add to the topic or to comment on the site and you can then do so by using SideWiki to leave comments that others can view. Being able to comment on a site from your web browser (specifically Firefox) is something other plugins have been able to do before, and what people using Google Friend Connect can already do.

So instead of displaying the most recent entries first, we rank Sidewiki entries using an algorithm that promotes the most useful, high-quality entries. It takes into account feedback from you and other users, previous entries made by the same author and many other signals we developed.

What they haven't mentioned in their blogpost is that it also provide Google more information about a site when it comes to displaying the site in the search results. I'm half expecting them to change their search results page slightly to show which pages have comments left on them, similar to how it's done in Google Reader. Also, as a site owner you can leave a comment using Sidewiki that is kind of a like a "sticky" in forums - it will remain at the top of the list of comments if you want it to.

In principle, and in these early days as it's first released it looks like a cool concept that may well add value to sites. I think it could provide valuable feedback for both site owners and for people visiting the site who are interested in more information and it could be a step forward in this area for Google. Though for businesses I can imagine the worry this could create - if some disgruntled employee or client decides to be constantly inflammatory about your site or business using this then it depending on whether it will filter abusive comments could well affect your business. If you're trying to win a big contract then chances are your prospective client will visit your site to find out more about your company, if they see many abusive or unsatisfactory comments in SideWiki it could well put them off even if it's only down to a "one off". In all fairness though I can't see this happening too often without it being deserved to some degree.

So far it's only available for Firefox and Internet Explorer but they intent on having it ready for Chrome soon. If you're interested in accessing SideWiki data to use elsewhere then they do also have an API available with documentation for JavaScript and Java.

I think before I can fully make up my mind on this one I'll need to watch how this one goes to see how it gets used by people and what affect it has on indexed content, and the value of the content on websites.

A brilliant move on Google's part to start aggregating the wasteland that is blog commenting in a place more closely tied to real identity (google's very own Profiles pages). Undoubtedly this will be tied into GoogleWave when it launches, sweetening the deal to include realtime updates. As a user, I love Sidewiki's concept and its elegant and non-obtrusive execution.

They are using what they refer to as "sophisticated language screening" to bury shit comments like "first" or "this site sucks" in addition to soliciting comment readers to vote whether or not any given comment is helpful. This goes a long way toward suppressing drivel, but I foresee 4chan or some other powerful community gaming it in short order. All it would take is an elaborate yet entirely satirical comment on mylittlepony.com plus a powerful crowd to back up the helpful voting process.

As far as I can tell, there's no way of disabling sidewiki for visitors to your site as a site owner (and I don't imagine that option becoming available since its against the best interest of Google). For this and other reasons, there will undoubtedly be a lot of site-owner backlash to Sidewiki.

Google constantly gets criticized for its intrusion into different realms where people perceive there to be a conflict of interest. I suspect they'll hold off on running ads in this overlay in the near-term to avoid being accused of cannibalizing ad revenue for content creators, but that may be their end game.

Unrelated to ad revenue, there's an entirely separate issue that I'm certain will concern many site owners. I doubt many blog owners and more so news outlets will appreciate the fact that they no longer have moderation control over comments about their site and the articles contained therein. Since these comments are disassociated from the site itself, there will be no more deleting unfavorable comments about your brand or business. For the vast majority of sites that don't allow commenting at all, Sidewiki provides an avenue for people to publicly air grievances despite that site owner's choice to disallow it. This has existed in one form or another in the past with things like StumbleUpon and, to a lesser extent, getSatisfaction, but Sidewiki takes it a step further by placing the comments effectively on the page itself, rather than on an alternate domain.

If nothing else, it will be interesting to watch the inevitable sideshow that ensues with this product's launch and how Google handles it.

This is sneaky ambitious.

Google is slipping this product through the backdoor onto millions of Google toolbars. It basically lets people comment on any web page, and all comments track back to the person's google profile. Comments are ordered by a number of factors including the "ProfileRank" of the poster.

It also aggregates back blog posts about the host url.

It's one part real identity play (like facebook connect), one part blog commenting (like disqus / js-kit), one part aggregator (like JS-Kit Echo), and one part Google Page Rank.

It's also encroaching on the domains of website owners - it's not hard to imagine Google running ads in the sidebar next to content owned by third party website owners. That could get ugly.