Does cancelling junk mail endanger your postman's job? I've heard it claimed that revenue from direct marketing pays the postman's wages, so we should all put up with a few items of junk mail or risk losing the postal service.
I don't agree. The marketers don't pay the postal service because they want everyone in the country to see their ads. They pay because they know that a few people will buy their products after seeing the ads. It's worth the money because of the increased sales. But most people don't buy the products, they just put the leaflets straight in the recycling. The marketers would love to know who are the people who will go on to buy the product and who just puts them in the recycling. They could save a fortune on printing the leaflets (and CD-ROMs, half-empty biros etc.) and still make just as many sales.
If you never buy products or services from direct marketing, you are doing the marketers a favour by cancelling, because it saves them money on which they get no return. And you are doing your postie a favour, stopping him trudging up and down your path even when you have no real mail. And you're doing the planet a favour by saving the resources needed to make, print, and drive around the country all that weight of unwanted mail.
Convinced? Read Reduce Junk Mail which has all the links to stop junk mail (and telesales calls) coming to your house. And don't forget to vote in the poll in the right-hand sidebar when you've done it.