Another way to look at it is that these well-known people coming onto Medium (which isn’t really a new phenomenon, by the way), are growing the whole audience. By doing so, they’re giving everyone a better chance to be heard. There is not a fixed number of Medium readers. And very few of the other places Michael Pollan publishes let you (or me) publish alongside him. Why not welcome all ideas and all people (famous or not) and let people decide what they want to pay attention to?