My understanding is a "scratched" or "spoiled" ballot is a waste and are not kept track of. However, you may "reject" your ballot by telling them you do not feel any of the candidates are worthy of your vote.
Rejected ballots are kept track of and should they receive more rejected ballots than votes for any of the candidates, a by-election will have to be held in which none of the original candidates are allowed to run.
It's a shame Canadian's don't know about this. It's basically equivalent to checking "None of the Above". I believe if the public was aware of this option that we would be able to send a far better message to our political leaders.
If I ever have the time and money to put into it, I would organize a National Reject Your Ballot Campaign to help Canadian's become more informed of this option.
A government should fear it's people, people should not fear their government.
Without me, it's only "aweso".