Why the assumption that a server connected via a patch cord will be better administered than a server connected by a dsl or cable modem or T1 line?
partly it's a question of scale. if a provider is terribly successful at this low end personal colo business they might have 10 racks of 40 customers per rack, such that they could quit their day job and just run this low-end personal colo business. which would be a 400:1 ratio between customers and staff, which is better than the 10000:1 ratio you'll see from your best-case dsl or cable isp. thus, a customer who neglects their server and allows others to use it as an abuse-staging platform, or a script kiddie who stupidly fouls their own nest by staging an attack from their own host, will get noticed by someone with clue, in nearly real time.
What you seem to actually be looking for is a connection with a fixed IP address which doesn't share "address reputation" with others.
no, i'm looking for a way to share address reputation amongst a group of serious-minded professional power-users who have learned over the years how to maintain their own BSD or Linux platform.
Why shouldn't an individual be able to operated a server on their DSL or cable modem connection?
because their provider is, statistically speaking, a money-grubbing slob.
Wasn't the original end-to-end nature of the Internet based on that?
why, yes, it was. but an implicit design criteria was that all of the users would always be as smart and as professional as the scientists, engineers, and educators who were the first generation of IP's users. (big mistake.)
Why prevent people from running servers on DSL and cable modem connections, yet say they could run an identical server in a colo?
because most providers don't want to give out static ip addresses, for one thing. because these providers are counting on a high suck:blow ratios from its customer base. because these providers know that people will pay more to get real internet access and they're holding you all for ransom. take your pick.
Why is one unsafe, and the other is considered Ok?
one is totally governed by a bilateral relationship between a 1U owner and a colo provider, neither of whom has a monopoly, and both of whom have something to lose if the IP address used in the relationship is abused. this isn't a technical thing. it's all about people getting what they want. -- Paul Vixie