coComment may go to open release tonight or tomorrow - it is still password-protected right now, Monday early afternoon - but it's already the talk of the whole blogosphere since Robert Scoble revealed its existence on Saturday. It's a free service developed by Swisscom Innovations and Ballpark (my friend Laurent Haug's firm) in Switzerland that lets you track all the comments you make on other blogs, as well as those of people responding to your comments, and so on down the conversation line.
Here is how it works: the first time you use coComment you install a "bookmarklet" in the browser, by just dragging a button to the bookmark bar (it works with Firefox, IE, Safari). From there on, you use it when you comment on other blogs: you enter your comment in the normal comment area of the blog page, and before submitting it you click the coComment bookmarklet. That allows coComment to make a duplicate of your text, including a backlink to the post you're commenting on, and upload it to your personal page on the coComment site. (If you don't have a blog, you can still have a coComment page and keep track of the comments you leave on other people's blogs).
At a later stage (they're still developing it) you will be able to share your aggregated comments with the readers of your blog by using another feature of coComment called "blogbox". Very much like with Google ads, this will incorporate a window on your blog where your comments on other blogs and follow-up responses would be dynamically displayed.
And of course an RSS feed of the whole will be available, so that you can get an "alert" in your aggregator whenever someone follows-up on your comments. (Blogs hosted by Blogger, MSNSpaces, MySpaces, TypePad, Wordpress and Xanga are currently supported, more will follow; see also the coComment learn more page and Laurent's own write-up).
So coComment may be opened up tonight or tomorrow as "beta" (as in "debugging by users") for everyone to use. It's a great and slick feature, and clearly one that addresses a real need of the blogosphere: how to keep track of a conversation. As I coincidentally wrote last week after a discussion with Scoble, the current tools of the blogosystem (blog ecosystem) are reaching their limits and need to get to the next stage, to start enabling a real conversation: one that doesn't die after a couple of comments because it is too laborious to track it.
Whether coComment will be the answer to this problem, at this stage I don't know. What I know is that the need for something like this is huge. After Scoble mentioned it on his blog, the info spread like wildfire (Swisscom and Ballpark didn't expect it, and they were not prepared: they've been trying to distribute "invitation codes" for people to test coComment, but clearly they have been overwhelmed - see this post by Laurent, and find my three remaining codes below). Many bloggers had been "hacking" their way into something similar, just by copying-pasting their comments or by creating ingenious designs. Dave Winer for example says (in a comment to this post): "What I do for now is generally when I comment somewhere, and I want to follow what’s said after that, is put a link on my weblog to the post: if it was interesting enough to leave a comment, I figure, it's interesting enough to blog". Dimitri Glazkov developed a similar idea called coblog, while Des Paroz bookmarks the posts he comments on in del.icio.us and tags those pages with the tag "mycomments": "I then convert the RSS feed of the del.icio.us tag" so that it displays into his mycomments page. Jason Kottke does it in a more manual way, by copying/pasting his most significant comments into his Further Afield page. And of course someone came up with a Wordpress plugin for just that.
Techcrunch points out that coComment doesn't centralize trackback comments (yet), while Valerie Thompson sees it more as a feature of Technorati (or similar) rather than a stand-alone biz.
If you want to check coComment before it goes public, go to the homepage and use one of the following invitation codes (they are single-use codes, so if one doesn't work it will be because somebody else has already used it - and I don't have more of them):