The point of mainstream sites indicating that the page has ajax with the URL path is to tell search engines. I have a feeling that what the author doesn't get is that it is very hard for search engines to tell the difference between ajax pages, static pages, and spammy keyword stuffed pages.

To me, it seems that Google recommends indicating ajax content in the path in the same way that our government issues concealed weapon permits. Yes it okay to have concealed content that can loads on the fly as long as you are very clear of your intentions. Once again this is a usability issue that wouldn't be an issue if it weren't for spammers.