John Gruber's critique of Trackback
makes some good points. And I agree with many of them. But I have to disagree with his central argument that you can use referrer data instead. This argument completely misses what I feel is the best use of Trackbacks: category-specific aggregation. Take Blogpopuli
, for instance, which uses Trackback to gather posts about weblogs. Each of the site authors who send Trackbacks to Blogpopuli would have absolutely no reason to link (create a referrer) to Blogpopuli every time they posted about weblogsit just wouldn't make sense to their post. By sending a Trackback behind the scenes, they let a subsection of the world know the post is about weblogs without changing the substance of their post. It's a subtle distinction, perhaps, but I think an important one. Using Trackbacks, we suddenly have a new service that simply points to distinct posts of a given category. Extreme-niche, category-specific aggregators can be set up using Trackback that just aren't possible with referrers or (non-categorized) RSS. And an open posting form
means even those who aren't using Movable Type can contribute.
Even with its current widespread use of Site A linking to Site B, referrers don't measure up. For a referrer connection to be made, someone has to click on the link. That may seem trivial, but it means less popular sites could be cut out of the loop. Referrers track what a site's audience is doing, not what the site's author intended. To make matters worse, the referrer will not point to the specific post that is relevant. For example, most people will click a link from this weblog's main page, and create the referrer: http://onfocus.com/
. As posts slide off the front page, referrer data will quickly become meaningless. Trackbacks use permalinks, which means the link will work well into the future. (Not to mention the problem most referrer-tracking scripts have distinguishing between http://onfocus.com
...they're the same site!)
There are also some cases were it's impossible for referrers to work. Check out the way Matt Haughey is using Trackbacks to keep a list of songs
he's listening to in Winamp. Because Winamp isn't a website, referrers can't exist. Extending weblogs into other devices requires a mechanism for transporting Web micro-content; Trackback could be that mechanism.
Sure, there are some problems with Trackback. And I think its current primary use of Site A notifying Site B of a relevant post isn't really its killer use. Topic-specific weblog post-aggregation is where Trackback could be very powerfuland relying on referrers isn't going to work to make that happen.