So, we've all heard about Google App Engine by now, right?
Well, here's a great example of how easy it is to make an interesting app, in a very small amount of code, on Google App Engine. And, have it be automatically scalable.
You'll notice that the blog is, in fact, hosted on Google App Engine. In under 100 lines of Python, there's a start at a perfectly functional blog engine (leveraging Disqus comments, which makes complete sense). There was no rocket science involved in what Bret put together. This is just the beginning.
Of course, this specific example lets you know how easy it would be for somebody to take on http://wordpress.com with a Google App Engine hosted solution.
And, this is just one, simple example. Forum software? OpenSocial apps? Software Project Management? Wiki?
I predict a sharp increase in Python and Django book sales. Enjoy the ride O'Reilly!