Wired has an article that discusses why the web is dead. To make their case they use this graph:
I think this is a little misleading as things like video and P2P are initiated (and encapsulated) by the web. But it's a good indication of where investment and innovation needs to go in terms of making the most of our networks.
Interestingly, a commenter from Boing Boing took the graph and reproduced it in terms of absolute traffic instead of percentages:
Which shows the dramatic hockey stick of growth. I'd love to see a corresponding graph of the capital cost for core network switches in terms of bytes/sec.