This excerpt taken from the AAPL DEF 14A filed Jan 7, 2009.
How are broker non-votes treated?
Broker non-votes are counted for purposes of determining whether a quorum is present. For the purpose of determining whether the shareholders have approved all matters other than the election of directors (Proposal No. 1), broker non-votes have the same effect as an AGAINST vote. The Company encourages you to provide voting instructions to the organization that holds your shares by carefully following the instructions provided in the Notice.