I wasn't even aware this was a thing until I went to pre-order mine last week and couldn't find them anywhere for my local theater, despite the number of movies premiering a month later which I could order tickets for.
Evidently, the problem was Disney studios was playing hard to get over contract negotiations with major theater chains like AMC/Regal, and was essentially holding IM3 hostage for leverage. Nice. At issue was the breakdown in profit split between theater and studio. With IM3 projected to make as much as 150 million in it's opening domestic weekend, a lot was at stake for both sides.
Well, in any case, pre-sales are a go on Fandango so if you've been waiting anxiously for your midnight tickets, now is the time to get yours.