This doesnt make any sense of course. At least not in re: to what Diest was proposing.
It would only ever come up if say, you'd have two posters like us, one of us would get banned and then the other one would not be able to post either. Which is a much smaller issue than what I was asserting.
Actually it's usually much worse than that.
In reality many times we'd need to ban the whole ISP to get rid of one user. For example AOL users often share IPs and for any one AOL IP there are often over 20 legitimate members here who use it. So any attempt to IP ban an AOL user would block many other people around the world who had nothing to do with it.
What makes it a bit pointless is that the user can just use a proxy and circumvent the ban in seconds while the rest of the good users are locked out.
IP banning is a tool we use rarely for this reason and it's usually reserved for computer security (i.e. dealing with robots who are trying to bring down the site).
On small sites you can get away with it, because you don't have enough traffic to run into the false positives you banned, but on larger sites this is problematic.
I edit wikipedia very frequently, and often find that I need to log in and use an account because the IP I'm on was banned for a previous user's spam or vandalism. Their bans are "soft" and you can just create an account to circumvent it because of this limitation.
What it all comes down to is this: the internet is based on fundamentally stateless protocols. It was not designed to even allow a users to log into anything and cookies were just added later to provide user state.
All methods of deriving state are optional to the user, so any attempt to get picky about identity requires guesswork and can be circumvented just as easily as it was put in place.
We'll still use it on occasion, but to think that it's much more than a temporary inconvenience on the banned user is to put way too much faith in it.
By the way nimh, I was wrong and after more investigation I now think your list is correct even though his posts are coming from many different IPs and locations.