Numerous devices and infrastructure services have the ability to expose location, but comprehending how to best make use of these technologies can be complex. Additionally, after the infrastructure is put in place, the next hurdle to overcome is understanding how to create a useable location-based feature that users can comprehend and love while also feeling safe and secure. This session is targeted to those who want to learn about these location technologies, and to those who want to understand how to think about their users' needs, their security, and their privacy. We'll also review web and mobile services that have been designed with location at their core, or location as a feature. And, finally, we'll talk about how Twitter thinks about adding "where" to our "when".