A friend of Seattlest sent us a link to Cakespy's examination of the history of the ubiquitous pink frosted cookie. Turns out "ubiquitous" only applies in the Seattle area:

If you don't live in Seattle, you might not even know about this cookie (while it exists elsewhere, we've never seen it in quite the same proliferation in our assorted travels); even if you do live in Seattle, you might not have stopped to question why it is that this confection is always around--gas stations, delis, grocery stores, drugstores--everywhere!

Turns out pink frosted cookies sprang, Athena-like, from the brain of Uncle Seth's Cookies, who sold their cookie biz to Mostly Muffins back in '96. They call it the Original Pink, and they're the reason you can pick one up when you're paying for your gas, refilling your prescription, or passing over Starbucks for your favorite local espresso vendor.

People have tried to recreate the recipe (secret ingredient: cardamom), but if you're not in the area and crave that pink shortbready goodness (or just want to buy in bulk), Costco can hook you up with an 18-pack.

Cakespy's theory about the pink cookie's success in Puget Sound?

In our minds, the first aspect is timing: the cookie got its start being sold in coffee carts just as the coffee business was starting up in earnest in Seattle; naturally, they would appeal for the same reasons that coffee is so popular in the area--the climate just begs for rich treats and coffee during those rainy days that take up oh, eight months of the year. The second and perhaps more important aspect? Duh--The frosting color. there's no secret that pink frosting tastes better than any other color.