There was a big debate a few years back about who should be responsible for junk mail. I believe that the companys pay tax or a levy on it now. If you don't want it delivered they have to pay to bring i back.

I remember some story about a guy getting junk mail and having the return envelope thing with it. He wrapped up bricks in brown paper and taped the return envelope to th package and the company had to pay the overweight charge on it.

Not sure it that was true or not