Is it legal to steal?

I was just wondering. It has happened for many years and it´s probably still happening as I write this. You see a new interesting product from the Clickbank database, you decide to buy the product. Instead of just clicking on the link and buying it, you change the hoplink to your own username at clickbank. This way you get to keep the commission from the sale and not the person who promoted it (the reason why you saw it). What I am asking today is; "is this legal" or "ethical" or whatever? I am not sure what I think about this issue. If I promoted the product I would like to earn money from it and keep my commissions. But again, if I saw a product I would still want to earn money from it, even though another person told me about it. When I sell clickbank products I always use an url cloaker, in case somebody would want to "steal" my commissions.