Sideways it's normal. You'd be surprise how often it happens.
What's not is when the plane hits an air pocket or turbulence, or heavy wind gush speed change on final approach or touch down.
That happen to me once in Chicago, on a pit stop on my way to San Jose.
Everybody simply shut up in the plane. The only sound you could hear was that old lady in the back filling up her depends. Had I worn one, I'd probably would have let go too.
-1 because although the video is nice, it's been all over the net in the past few days and... well... you dont see anyone craping their pants.
A lot of planes are being forced to make emergency landings because the airlines are underfueling to save money. A couple of weeks ago I was on a coast to coast flight that was forced to land and refuel.
The great thing is that the passengers on the right side of the airplane may not have noticed. That is, until the sound of wing metal striking tarmac...