In Disney world (not Disneyland yet), the first time you use a ticket, some biometric info (certain finger lengths) will be collected and stored. It's said that they will do some comparison next time the same ticket is used again. If you buy a used ticket from ebay, in theory you might not be able to use it. But I heard many people were able
to use the tickets that were previoulsy used by other people.
to use the tickets that were previoulsy used by other people.