We’ve released a WordPress Plugin which automatically archives anything you link to in your blog posts; it also adds a ‘perma-permalink’ for the archived version adjacent to each original link.
An Amazon Web Services case study put me on to Hanzo a while ago, and in May 2008 I actually spoke with Mark Middleton (the markm who posted the entry above). Mark revealed that community take-up on the plugin and other general purpose web archiving services was below expectations. The company has since refocused on legal matters (even their blog tag-line has changed to “web archiving for compliance and e-discovery”).
I wonder if, now that the number of people and companies that have been blogging for years has grown, there might be more of a market for such a service.