In perhaps another sterling demonstration of the effectiveness of Google's own product announcements by way of its blog posts, the world awakened this morning to an experimental capability in Google's Gmail that, if you think about it, you wonder why no one's thought about it before: An independent developer with the handle Yuzo F is distributing a Gmail add-on that gives users five seconds after clicking on the Send button to click on an Undo link that stops distribution from going forward.