In discussions about Peak Oil, one of the criticisms often leveled at economists is their assertion that substitutes for oil will be available. Some of the economists may mean that in a strict liquid-fuels sense, and most of the Peak Oil crowd interpret it in a strict liquid-fuels sense, but it's important to think about the statement in a more nuanced fashion. That is, that there will be substitutes for goods and services that are currently oil-powered, but in an indirect fashion.
Almost 20 years ago now, I wrote various prototype applications that supported multimedia sharing over the Internet transport protocols (TCP/IP). The emphasis was on the kinds of media that got used regularly in technical meetings and classes: audio, an overhead transparency projector, a whiteboard, page-by-page looks at documents, all with various mark-up and pointer capabilities. There was even some of the world's worst live streaming video. OTOH, in that sort of situation, the primary purpose of video turned out to be the ability to do out-of-band body-language signaling (I'm bored, I'm excited, I have something to say), and video can be remarkably bad and still convey those messages well. The software used IP multicast where possible to reduce bandwidth needs. There were a variety of control modes, since the needs of a small group of equals are different from the needs of a distributed classroom.
The main point is that substitutes are not always obvious and direct. A lot of oil is burned to enable some form of communication. There are alternate forms of communication that don't need to use oil, or at least not nearly so much and not so directly. And I'll be the first to say that multiple media over IP is not a substitute for all forms of personal communication; there are situations where face-to-face is much better. There will be other situations where liquid fuels are being used to provide a service that can be implemented in some other fashion. So "substitutes" for petroleum-based liquid fuels doesn't necessarily imply drop-in liquid fuel replacements. That's an important point to keep in mind when considering how things might unfold in the future.
Technical notes on the video shown above:
240x184 pixels, one-bit color depth (real black-and-white), 15 frames per second. At the time, many of the computers, even in an R&D setting, had one-bit monochrome displays and quite limited processing power. This particular coding/compression scheme had the advantages that it could be displayed directly on such screens while putting very little load on the processor. An individual image looks worse than the moving video; the human vision system does a lot of smoothing when there's motion going on. Only "moving" parts of the image were immediately updated; the background filled in gradually. It was somewhat surprising how much information was conveyed: body language, facial expressions, etc. It was easy to tell if the audio was properly synchronized (it was, a claim that several very expensive conferencing systems that came through the building for evaluation a couple of years later couldn't make).