I found it seems B-2 visitors don't need to fill I-94 freecall2013-09-02 16:31:00

I found it seems B2 visitors don't need to fill I-94 hard copy any more,
the CBP just scan their passport and can print out the I-94
number later, yes, I went ot their website and can't print out yet,

so my current question, do they scan their passport again when they depart USA,
so we don't need to turn in the I-94 hard copy anymore? very confused now.

Thank you for your help.