I've noticed that once you cast a vote, there is no way to change it. What if you were to accidentaly click on the wrong number?! Earlier today I went to give an image a vote of 7, but moved and ended up clicking on 6. I know that is not that huge of a difference...but it would be nice if I could have revised it.
In order to change a vote the system would need to know what your first vote was. It doesn't save a record of how each person votes though: only the average and number of votes. I considered it an acceptable compromise since the instances of mis-votes are very infrequent.
This is a little off-topic, oh great one, but I was curious...
Seeing as you can't vote more than once on an image, the database must record the fact that you have voted previously on that piece of work (though not the actual vote value). Presumably then you could always tell exactly who had (and had not) voted on an image?
"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." Bertrand Russell
the problem with it not recording the value is that if you wanted to change it, the system would not know which previous value to remove, you could have voted anything.