A few problems I have with the built in blacklist in wordpress is that 1) it's not alphabetized, and 2) it allows duplicates, 3) as well as spaces next to each listing.
I wrote a little script that will clean up the list – which you can load directly in a browser (change extension to .php and upload to your wordpress install directory) – it will clean up and then update your list – however, it would be great to integrate this directly into WordPress. Anyone have any ideas where it would go, exactly?