Interesting Fact About Junk Mail

While reading the Straight Dope, I ran across this neat little tidbit:

“..of the 161,000 people who wrote to the DMA (The service that keeps a do not mail list) last year, 116,000 wanted more junk mail. They were sent a booklet entitled “How To Get More Interesting Mail” (as God is my witness, I am not making this up), which tells you various key catalogs that you can send for to guarantee you’ll be deluged with stuff.”

Interesting. Who are these people?