Digital social media have transformed how we communicate and manage our relationships. Despite its portability, sketching as a social medium has been largely left behind. Given sketching's unique affordances for visual communication this absence is a real loss. Sketches convey visuo-spatial ideas directly, require minimal detail to render concepts, and show the peculiarities of handwriting. Sketching holds the promise to enrich how we communicate, and its ubiquity is critical for sharing information at opportune moments. We present the results of an exploratory field study of ubiquitous sketching for social media, documenting users' experiences with UbiSketch. This system integrates digital pens, paper, and mobile phones to support the transmission of paper sketches to online services. We learned that UbiSketch enabled participants to leverage sketching's unique affordances, that ubiquitous sketching creates a synergy with the practice of posting context-dependent information, and that it broadens and deepens social interaction.