I wrote on Twitter recently that cupcakes are a metaphor for everything that's happening in modern cities. I was only half serious, but it still sorta worries me. I have to admit, I love cupcakes. The cake in a cup store in Tremont is like my personal version of the siren singers. Just the same, I can't help but feel a twinge of middle-class guilt every time I step inside. Of course, there are many reasons to love cupcakes. They are delicious. They are sold by local small business people in walkable, urban locations. They add to vibrancy to once downtrodden neighborhoods. In that sense, these stores have a psychic significance in the community that goes beyond its (no doubt minuscule) economic impact.