All,
In my opinion, it would be very helpful if sidebars had the ability to
perform validations on the admin side. I mentioned this to Piers on his
website, and have now created a UserStory to go along with it:
http://www.typosphere.org/trac/ticket/830
From the perspective of building a friendly blogging system, it would
make sense to build in some sanity-checking where applicable.
Comments anyone? I’d be keen on doing this myself, but I’m not sure how
in-flux the sidebar code still is, and I don’t really have any free
cycles at the moment 
Paul