There is a very interesting posting on http://moneyversusdemocracy.wordpress.com/2014/02/14/time-to-democratise-building-societies. It is about electing building society directors but the most relevant part for STV supporters is an explanation of how block X voting works.
Block X voting is used to elect many building society boards, local authorities, pension trustee boards and club committees. Several vacancies are filled together and each voter is allowed as many votes as there are vacancies.
The problem is that, if there are, say, four vacancies, a voter who uses all four votes casts one of them for his favourite candidate and the other three against her.
The best short-term solution for the individual voter is to use only one of the votes. The best long-term solution for voters generally would be to change the voting system to the Single Transferable Vote (STV).
STV Action 