Wasn't trolling, I had seriously never seen this before. I never noticed it on my older Gary Fisher mountain bike, and there is zero wobble on my wife's Trek 820. A couple random bikes I looked at yesterday didn't wobble either.

Because I'm so OCD, I pulled off the cassette and brake disc to get a good look at it. It appears that the hub is what is is wobbling, I guess due too poor machining as explained in Mrrabbit's video. Here's another video:

It is wobbling enough that it makes the chain pull on the crank and moves it back and forth close to 2mm. That's really annoying to me, but if you guys say it's normal, I'll try to get over it.