I saw this pop up on my phone yesterday.  I had to try it. Are you using it yet?

I went to Facebook help to get the instructions on how to add a video to you profile pic. It's pretty easy: Check mine out here. It seems to play in a loop with no sound til you click it.

FB VID1
loading...

This feature doesn't seem to be available for business pages yet but I'll keep an eye out.

Here's how Facebook explains how to get started:

You can take or upload a video of up to 7 seconds to use as your profile video. Profile videos appear at the top your profile just like a profile picture. You can currently only add a profile video from iPhone or Android.
To add a profile video from iPhone:
  1. Go to your profile and tap your profile picture or video
  2. Tap Take a New Profile Video to take a new video or tap Upload Video or Photo to choose a video from your phone
  3. Tap Next, then tap the bar at the bottom of the screen to choose a thumbnail for your video
  4. Tap Save
To add a profile video from Android:
  1. Go to your profile and tap your profile picture or video
  2. Tap Take a New Profile Video to take a new video or tap Upload Video or Photo to choose a video from your phone
  3. Tap Next, then tap the bar at the bottom of the screen to choose a thumbnail for your video
  4. Tap Use
Note: Profile videos are public and can be viewed by everyone.
This feature isn't currently available in all locations.