No show after reservation with JR Pass

What would happen if a JR Pass holder makes a reservation but fail to board the train at the scheduled time? Is there a fine or penalty fee? Can another reservation be made for the same route?

Trakarn,

There is no penalty, and you are free to make another reservation, but if enough people continue do this, it is quite possible that JR could consider introducing restrictions or charges on reservations by Japan Rail Pass holders (as happened with JR East's Shogatsu Pass).
As your unused seat prevents someone else from getting a seat, please make the effort to return your reservation if you know you won't be able to use it.