The document summarizes trends and challenges in delay tolerant networks (DTNs) or mobile opportunistic networks. It discusses the history and motivation for DTNs, which allow communication in disrupted environments without continuous end-to-end connectivity. The talk outlines common DTN routing protocols like epidemic routing, PROPHET, and spray and wait. It also presents example DTN applications for emergency response, wildlife tracking, and rural connectivity. Key challenges discussed include routing, mobility models, and leveraging social network properties for more efficient opportunistic communication.