. . the big boys used to be the only option when you stepped into a store in search of running shoes.

" As bike-industry marketing speak goes, the "radio" analogy was about as weird as I'd seen. But this month, while riding a new bike from Jamis called the Commuter 4, I could see the connection. The shifting on this city bike does not involve traditional gears.

Back then these large-tire bikes were made only by custom frame-builders who liked to pedal in snow and a single Minnesota brand, Surly Bikes, which mass-produced the first notable bike in the "fat" genre with its Pugsley frame. Wide rims, extra-large tires, and weirdly-dimensioned frames to make it all fit together define a fat bike, a cycling subcategory that's garnered a serious following now in 2012. Bike shops report selling out of fat-bike stock.

Dear EarthTalk: What is the “Fair Trade Your Supermarket” campaign? -- Brian Howley, Washington, DC A project of the non-profit Green America, the “Fair Trade Your Supermarket” campaign aims to empower consumers to advocate for more “Fair Trade” products on store shelves at their local supermarkets.

Dear EarthTalk: Why is Greenpeace upset with some leading tech companies for so-called “dirty cloud computing?” Can you explain? -- Jeremy Wilkins, Waco, TX Leading tech companies like Google, Apple and Microsoft are now offering unprecedented amounts of data storage and access to “apps” on huge Internet-connected servers, saving consumers and businesses the hassle of installing and running programs and storing information on their own local computers.

Dear EarthTalk: How is it that dams actually hurt rivers? -- Missy Davenport, Boulder, CO Dams are a symbol of human ingenuity and engineering prowess—controlling the flow of a wild rushing river is no small feat.