First, I agree with what Xeno has said. I just want to add more because I love this stuff. It brings me real comfort.

Jacob gave this prophecy of the tribe of Dan:

>Dan shall judge his people, as one of the tribes of Israel. Dan shall be a serpent in the way, An [l]adder in the path, that biteth the horse’s heels, so that his rider falleth backward. I have waited for thy salvation, O Jehovah.

The tribe of Dan had trouble establishing a place, in the conquest of Canaan. Today, you can see a serpent trail of 'dan' named places, from the Danube River to the land of the Danish above.

But that's a weak argument. A little loose. So here's this:

Revelation 6 is of the four horsemen (the rise and fall of the Roman Empire).
The next chapter, Revelation 7, lists 12 tribes of Israel, naming them as "those that came out of the great tribulation" (the four horsemen just listed)--but Dan is not listed among the 12 tribes (instead the tribe of Joseph is listed in full by its two parts, making 12). Why isn't Dan listed?

Because Dan has not gone through the tribulation (the rise and fall of the Roman Empire). Dan was the Germanic tribes above. Dan was the stone that judged their fellow Israelites. He biteth the horse's heel. He had been a serpent along the way.