Whilst watching the current London Olympics I noticed that out of the 10 scores shown for each dive in synchronised diving, a few a crossed out each time.
Why are a few of the scores always crossed out?
The short answer: to prevent a judge from manipulating scores.
The highest and lowest scores are discarded (crossed out) and the middle scores are summed, weighted by 3/5, then multiplied by the degree of difficulty.
For London 2012, each overall score will be based on a middle score for each diver's execution and three middle scores for synchronization.
FINA defines the structure of scoring in diving here.