In 2007 I built a text highlighter service for the web. It was really as usable as it could be : you click a button and start highlighting text in the page. At the time social bookmarking was still relevant and my web highlighter was a better social bookmarking. But by examining usage patterns, I quickly realized it's a dead end : keeping things organized is work. Apart from nerds nobody would take the time and have the discipline to keep things organized outside the context of work. Once I realized that I knew del.icio.us which I was using every day is doomed. And I think that travel planning software is doomed for the same reason not because use frequency is low. Leisure is the wrong context for planning software.