Rob Brewer wrote:

This is a good policy, except that (as far as I can tell) when you check contribs for an IP address you only see edits made anonymously from that IP, but when you ban an IP you ban both anonymous and signed-in users at that IP. If a proxy or a shared computer has been used by an anonymous vandal and a useful signed-in user, the signed-in user will be blocked, and Wikipedia will lose the benefit of his edits.

Has anyone thought of selective banning?

Refuse anonymous edits from the banned IP, but allow signed-in edits.

We could supply a message like, "Sorry but due to abuse from IP i.j.k.l, you must sign in to contribute."

Ed Poor