More precisely: Creating a Chrome extension that functions just like a bookmark on a fixed web page [EDITED to clarify: that is, one whose content is fixed] is almost as easy as just making the web page. In other words, "hello world" is easy.
It's nice (and maybe important) for "hello world" to be easy, but this really says nothing at all about how easy it is to make an extension that actually extends the functionality of Chrome.
Adding hotkeys to HN was relatively painless from the set-up point of view. Of course it doesn't do any heavy-duty message passing, but I suppose it could be a good example for those who want to build something that is heavy on the content script side of things.
It's nice (and maybe important) for "hello world" to be easy, but this really says nothing at all about how easy it is to make an extension that actually extends the functionality of Chrome.