If you watch the video above, from Sebas & Clim, you may notice that the client logo has been pixelated out. As part of their contract with whomever the client is, Sebas & Clim can show the video without voice over or brand logos. It is a neat way to get to show your work when a client would like to keep it under wraps. A side product I found of having no voice over was that I focused more on the great animations and production of the piece.
You can read a more detail on the subject of 'How To Make Sure You Can Show Work In Your Portfolio' over on motionographer.