The color choices (dark font on dark grey background) and excessive gradients lead me to believe this is fake.

Yep. And the screen looks strange in nearly all of the shots.

and the fat "iPhone" font on the back of the phone is not right.

Also, the renders are poor quality, they show a device which is not likely to be able to fit an adequate battery, and which is not likely to be comfortable to hold.

The link just proxies http://www.youtube.com/watch?v=jxYnuHX3LCI The video shows someone clicking through the German Apple website, "discovering" German pages for an alleged iPhone 5. It is fake, as several people on YouTube pointed out. Most notably, in the first frame of the video you see a local URL in the browser's address bar. Additionally, there are some spelling errors in the website, like "Grösserer Display" instead of "Größeres Display".

Your last argument is not quite correct: He's faking the swiss-german site, seen in the URL as /chde. While grammatically a little bit on the shaky side ('Der Display' is rare, but not unheard of, and actually wrong.), the Eszett doesn't exist in the swiss alphabet.

Apple's iPhone 4 promos all show full bars + 3G in the corner, these show "No service".

Everyone knows this is fake, right?

I'm not so sure bout this one, the design of the phone looks a little unrefined.

I don't understand the appeal of making all of these fakes. It's not like this guy/gal is getting ad revenue for us watching this video...

The most amazing thing about this video, if it were real, would not be the specs of the iPhone but that it was launching in Germany before the US.

Good find, it looks pretty slick if it's legitimate.