1. A method comprising: receiving, from a user computer, an indication of text displayed on a display of the user computer; determining, by a computing system, advertising content for transmission to the user computer based on at least the indication of text displayed on the display of the user computer; transmitting, from the computing system, a request for the determined advertising content to one or more computer system nodes of a network of computer system nodes, wherein the computer system nodes are configured to: dynamically determine, for advertisements received at respective computer system nodes, one or more forwarding nodes of the computer system nodes based on one or more statuses of the respective forwarding nodes and/or one or more statuses of the network; continuously forward the advertisements from respective computer system nodes to respective determined forwarding nodes without storing the advertisements on any fixed storage medium in the network; and providing the determined advertising content to the user computer.