Karl Auerbach posted an item in his CaveBear Blog on 19 August that is still important reading:
"I am always amazed, and appalled, when I fire up a packet monitor and watch the continuous flow of useless junk that arrives at at my demarcation routers' interfaces... [I] believe that this background noise will become a Niagara-like roar that drowns the usability of the internet. "Between viruses and spammers and just plain old bad code, the net is now subject to a heavy, and increasing, level of background packet radiation... Search engines still come around sniffing for web sites that disappeared... I am aware of people who are continuously bombarded by file access queries because a prior user of [their IP] address shared files from that address. Entire blocks of IP addresses are also contaminated, perhaps permanently, because they once hosted spammers thus causing those address blocks to be entombed into the memories of an unknown number of anti-spam filters not merely at the end user level but also deep in the routing infrastructure of the net....
"I believe that something radical will happen: We may see the rapid end to the 'end-to-end' principle on the internet... The loss of open end-to-end communications will, in itself, be a great loss. But of even more concern will be the fact that these portals, or gates, will require gatekeepers, which is merely a polite word for censors..."