The ejection occurs in the skiinning mode, especially with Burton PSI's (anyone want to buy a pair?) With the PSI's the lever is much bigger. And if you hit it with the other half of the split, it releases. Believe me, it happens often.
With he regular SI's the motion is in the other direction (up) and the lever is smaller. So, its not so easy to do. It happened to me only once. But that still sucked!