"Spoling" the ballot means that it won't be counted.

Not true! From that source of all reputable information, Wikipedia...
(Although I do believe this one to be true.)

"The validity of the election may be questioned if there is an unusually high proportion of spoilt votes, however, in countries such as the UK where a spoilt ballot paper counts towards the voter turnout, some voters will deliberately spoil their ballot paper to show disapproval of the candidates available whilst still taking part in the electoral process. In theory, a UK election could have a 100% turnout with no votes cast for any of the candidates if every registered voter were to spoil their paper, although this is highly improbable."

I also believe that the spoilt papers can and often are read by the candidates to confirm that the vote was or was not for them. So a cross in the box with a comment of "I would have voted for you had you not been such a greedy lying bastard." could indeed make a point.

Cheers

DeG