I read all the comments, and have a totally different point of views. Yes, twitter needs to innovate more. You need to make a number of changes to the user interface and give more options. But I think that for now, the best and easiest thing they can do to bring back most users is to give more power to his Big Players. Help than make more money, be more promoted, have more publicity in twitter than any other social network. Stop thinking that promoted hashtags and other options that are only used for spam have a great return for the sponsor. Celebrities, players, journalists, politicians. People want to talk to them and twitter is the best media tool for this.