It's not hard to see why after looking at other video formats people prefer on the road: raw HTTP video (19.2 percent) and Facebook (8.6 percent) were the next-closest, which suggests that many still grab snack-sized videos on their phones instead of full movies or TV shows.
Similarly, Facebook and Twitter send login credentials over a secure line and then revert to an unsecure protocol. (Users of those social networks can add an "s" after "http" to force the systems to encrypt their browsing.) Social networking sites are where people increasingly conduct private conversations, whether through Facebook's Messages or Twitter's Direct Message feature.