Why do you get to decide that, I can't, from a hotel room, call my ISP and put up a web server on my dialup connection so someone behind a firewall can retrieve a document I desperately need to get to them? Why _SHOULDN'T_ I run a web server to do this over a dialup connection? Why do you get to dictate to _ANYONE_ what things they can and can't do with their most portable internet access? How can you say that it is negligent to refuse to DOS your customers unless they request it? (blocking traffic to me that I want is every bit as much a denial of service as flooding my link).
The distinction may be blurrier these days, but there *is* a difference between networking and internetworking. Whereas I'd agree that interconnections between networks be unencumbered to the greatest degree possible, the administrator of a network can be slightly more draconian in order to keep the network running smoothly. This statement applies, IMHO, to any provider who sells service to individual users. It may be a huge wide area dialup network, but it's still a network, in which the average customer is not a professional network administrator but rather a user of indeterminate knowledge level. Now, if as an ISP you operate an internetwork ("network of networks") and a network of users, the challenge is obviously how do you draw the distinction between user/customers and network/customers. I think it's do-able (DHCP being one criteria that comes to mind), but there there are a lot of permutations to consider.