We introduce spotcast, a new communication abstraction specifically aimed at the development of mobile proximity-based applications running in mobile ad hoc networks (MANETs). Our motivation lies in the fact that traditional communication abstractions, typically broadcast primitives with strong consistency guarantees, do not adequately capture the intrinsic here-and-now nature of such applications. Rather, developers need a communication abstraction offering the notion of proximity-based diffusion and some level of message durability, which is precisely what spotcast provides. We illustrate how spotcast can be used to implement mobile applications and we shortly discuss the correctness and the implementability of the spotcast abstraction in MANETs.