This is just my opinion from Disneyland Paris - we were in the Town Hall (guest relations) as we were having a private tour and had to wait a while so I saw quite a few disabled people come in to get their passes. I can honestly say I don't think any of them were cheating the system as they had to bring a lot of paperwork to prove that they were disabled "Medical certificate: guests must present an original medical certificate in French or English issued less than 3 months previously, signed and stamped by the doctor and testifying that they have a disability or debilitating illness, or are pregnant." There are also two different types of cards (I don't know if there are in the US?) so that if you are not registered disabled (IE you've broken your leg) you can still enter rides through the special entrances just not cut the queues.