Excellent suggestion, one nobody will have thought of up to now. There are of course a few problems.
Techie: We've got another one boss, traces back to Birmingham Central Library
AB ED: Ban Birmingham Central Library
Techie: OK boss. This one here too, it's from the BBC
AB ED: Ban the BBC !!
Techie: All of the BBC ?
AB ED: Yes. By the way I thought you were on jury duty today ?
I had emailed the tech team and they replied and said that they're looking in to ways they can limit people have various user names but in the mean time to report them!
All dial-up users (and many broadband users) have dynamic IP addresses. (i.e. they have a different IP address every time they log on to the internet). So the suggestion is simply unworkable.