Tantek Çelik ponders modifying permalinks to recently posted material:
If a permalink anchor changes and there was no one hyperlinking to it, did the permalink really break?
There's no way, of course, to be absolutely sure that a document is un-linked. Referrers are the only universal, immediate record of a link, and they're only sent once the link is actually visited. The moral: always follow the links you create and keep URLs cool by not changing them.
Tantek's weblog structure overhauls are instructive despite this minor indiscretion -- and the koans are free. So far: better URLs -- but still no slugs -- and an XFN enhanced blogroll. If you haven't already, view his source for an anatomically interesting weblog post structure (built using (X)HTML lists).