<p>"Would you like some chocolate?" Timothy Childs, standing on a sidewalk in Noe Valley on a recent Saturday, offers a small piece of candy to a passing shopper. Because it is summer in San Francisco, Childs wears a parka and an exuberant polar-fleece hat covered with bouncing fuzzy tendrils. The passerby, her own polar-fleece jacket zipped up to her lips, keeps walking.</p>