Letters or Infomercial?

The letters read on All Things Considered included a long one about one listeners obsession with Fritos Flaming Hots! Can NPR really justify singling out this superficial letter from the many letters and emails they surely get on weightier topics--such as the assault on the Constitution by Bush and Co., the debacle in Iraq, the coming debacle in Iran, etc.? If anyone knows how do they decide on which letters to read on the air, I'd love to know.