I think that celebrities are in a bit of a bind, as to deciding which charities they should support. In your article you mention how one of Justin's tweets created a surge of donor transplants. This proved greatly beneficial for the ottawa woman who needed a lung transplant. But what about the millions of people who aren't privy to his grace. Due to his superstar platform it would be impossible for Justin to help every single person in need. On the flip side, is it actually too much to ask to say celebrities should be completely and unconditionally indebted to the millions of people who lifted him to the status that he is?
Most people can tell when a celebrity is just making a appearance or singing a song to promote them selves as an artist. It is also clear when a celebrity takes steps to ensure that they help change the world for the better. A great example of this is Justin's Believe Charity Drive. Justin puts his celebrity status in the hands of regular citizens to take initiative and create a fundraiser of their choice. This site has gained awareness for copious issues. This all may be a political move for Justin, but in hindsight lives are being helped and saved so all is well in the world of popular culture. This is a contrast from the popular superstars who use their riches for there gluttonous means.