In 2011 long intros were huge on youtube, with all the visual effects and music galore! Now 4 years later, less and less people are using them. On one of my old channels I had a 25 second intro but since I moved my current one I use an outro. Before my video goes to the end card you see my channel name come up. I've always stuck with that because like many of the other guys have said, it's about the first few seconds to grab the attention of the audience.