The fact that the Occupy Movement doesn't have leaders is one of the best things about it as a grassroots movement. It's also something that may prove problematic as it moves forward into a future where the encampments are no longer a mobilization base for struggle. Having some leaders, a steering committee or something similar, is going to be needed eventually especially if an entity, like a new political party, is going to emerge.
But it's true that the concept of leadership brings with it its own set of problems. When actual people are selected to embody a movement, it evolves from an all-encompassing, nebulous idea to a tangible reality. A leader, even a slate of leaders, cannot possess all qualities the 99%.
They each will have an age, a race, a gender and sexual orientation. The very act of selecting leaders is exclusionary by definition and the one thing the occupy movement has successfully avoided is alienating any one segment of the 99%. Once a leader or group of leaders are elected, appointed, self-selected, drafted, cronyism has the opportunity to germinate. It may be subtle but it appears to be human nature, not just in politics.
Look at the capitalist workplace. Studies have shown that managers tend to employ and surround themselves with people most similar to them. That's how empathy works in this rat-race culture. The more someone's character traits and values match your own, the greater your ability to identify with both their struggles and accomplishments.
Still, while consensus and absolute democracy may work fine in small groups, they can't function on, say, a nationwide scale. Leadership will be a key issue in organizing and one that will have to be grappled with sooner or later unless a truly innovative and radical structure can be formed. I have no idea what that would look like but within an upheaval where everything is new, anything is possible.