There have been multiple applicants scheduling two examiners for their check ride and then canceling last minute or "no-showing" with one of the examiners. This isn't cool! Not only is this unfair to the examiner, it also screws other applicants who want to get their check rides done.
All examiners are required to notify the FAA of their check ride schedule at least 48hrs in advance. This is usually how we discover someone booked another examiner. The FAA usually (but not always) let the examiners sort this out. In my case, I will make it simple. I will call (or text) and cancel your check ride with me and will not let you reschedule.
Some examiners have discussed charging a scheduling fee. Basically, the thought is to charge your credit card $100 when the check ride is scheduled and then apply that towards your check ride fee when you show up. For example, if the check ride fee is $450, $100 will be charged when you schedule and you'll pay the remaining $350 when you do your check ride. If you no-show or cancel short notice without rescheduling, you lose the $100.
I hope it doesn't come to this, but it may if this double booking thing continues.