A few months ago the ability was added to limit IP blocks to allow logged-in contributions to continue. This allowed finer-grained blocking of troublemakers on shared IPs (schools, AOL etc).
There's some suggestion to make this the default mode. I wanted to announce this ahead of time since it will change what happens when admins make a block without manually clicking something extra.
If there's no serious objection, we'll go ahead and change this in a few days.
-- brion vibber (brion @ pobox.com)