This is going to be a rant. I'm just a bit frustrated.
When organizers work hard to assemble an event, and speakers submit to speak, we are grateful for their time and effort because that makes our events.
That being said, when I submit to a conference to speak, I am 100% sure I can make it before I submit and that my schedule is clear. I never submit to more than one conference in a weekend or week.
Jacksonville has been one of the largest SQL Saturday Conferences for years, and we typically have 11-12 tracks and 50+ speakers. We don't usually turn away speakers because of the diversity of topics and the availability of rooms and attendees.
This year we had multiple speakers submit to our event and another event on the same day, then after our call for speakers was closed, and the schedule announced less than a week later, multiple speakers said they could not attend because they had been selected for another conference that same day.
I'm not sure if the speakers forgot they submitted, but if they were selected to speak at another conference, they should have notified and withdrawn immediately or not submitted to two on the same day.