TL;DR: URLs matter; we as developers need to make them relevant again; hiding them is a terrible idea
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I guess this goes to the app-ification of the web.
There's a dangerous slippery slope here. If we're OK with this happening, are we then OK with getting rid of that domain further down the line? What about routing all traffic through Google first so it can check if a URL is "safe" or not. The whole thing strikes me as creating a more locked-down web.
URLs and View-Source are fundamental elements of the vision Tim Berners-Lee. WorldWideWeb, the first web browser had it front and center. Mosaic moved it to the top, where we most know the URL scheme to exist. Safari moved the URL box to the same line as other navigation (what is now more common). Every step of the way, the scheme has been getting reduced for usability purpose.
But the problem with that approach is that it communicates that the web is "hard" instead of educating users in how to understand it and how to build on it.
And we, as technical people have not helped much here. Look at the URL up here. Yes, we know that it's hacker news but what does the ID mean? It has no semantic meaning to a user (unless you know that this is the 7678580th story on HN and care about that). A nice URL would be something like http://hackernews.com/story/google-experiments-with-URLs
Wordpress actually does this by default, even adding a date scheme to it, which makes the web a better place:
http://site.com/year/month/day/story-title-can-go-here is an easy to read URL and yes it's a pain to code properly when you're dealing with a dynamic site but hey it's our jobs to make sure we do things that are beautiful for users.
So maybe this is a wake up call.