I don't think you should make assumptions about why an individual chooses to support an organization or cause just because they are a "star". I'm sure some celebrities do it because their agent tells them to, but George Clooney and Don Cheadle have put a lot of personal time and energy into working for peace and justice in Sudan, even putting themselves at personal risk to do so. Celebrities can do a lot to bring attention to important issues by lending their name, so even if they are not so passionate about it they can do a lot of good. What are you doing that qualifies you to pass judgement on others? If you're going to judge others, do it by their actions, not their supposed intentions.