If widely adopted, this could be very useful for holding politicians, corporations, government agencies, or other powerful/influential/public individuals/groups accountable for their statements. It is common practice for such entities to change their websites and then act like their new positions or opinions were the ones they had held all along. We already have tools (e.g. Google's cache) catching weasely acts like this, but a tool like this would make the job a whole lot easier.
Unfortunately, it looks like it only works if the website's owner implements the framework, and the weasels have very little incentive to do so.