Vested Interest - Mad Men

We watched a short fragment from Mad Men and we took it as an example of vested interest in companies, in daily life.
 To begin with, what is vested interest? Is the interest of someone in influencing something so that you can continue to benefit from it, it can include the distortion or hiding of information.
Where can we find vested interest in this scene? In Don's idea, when he proposes to sell to the public something that is harmful, but not to inform the audience. He is hiding some of the information, wich if people get to know will affect the selling, so Don avoids the truth and tries to get profit from this. But before, we can see a previous proposal, Peter's. And why is it rejected? Simple, Peter in his idea accepts that the cigarrettes are harmful, and that soon or late people will die. He says everything is dangerous in this world, including cigarrettes, but for Peter, people doesn't have to worry and enjoy life.