Scanner sharing service stops after logout. How do I make it always share?
You might have to set up a default user that logs in automatically and shares the scanner after a reboot. You could have it password protected, non administrator, with a short timer on the screen saver to lock the screen after a power failure if you care about that sort of thing.

Snow Leopard just doesn't mount external drives or start the sharing software when a user is not logged in.

I have long kept around an old mac mini to serve up iTunes and a scanner for my network rather than mess with a "fake account" as I proposed.