7.5 Side to side play in axle

[philzilla]

Today I was working on my truck and noticed play in my axles. I can moved my tires side to side 1/4"-1/2". It does this on both sides equal amounts. Maybe the C-clip play?
Here is a video.
http://youtu.be/fYbLKgWug1I?hd=1
My question is, Is this normal movement.

 

[Sunk]

In the video it looks like the tire moves less than 1/4", more like 1/8" or so. That's normal.