When we left the US last week, my husband (Australian citizen) had to be entered into the computer and fingerprinted by the Dep't of Homeland Security at the gate of departure. He was given a little white receipt (like a NYC taxi receipt) which he had to turn in along with his I-94. Now they will have it in the computer when you leave, so I think turning in the I-94s may become less important.

The only problem was they weren't very vocal about the requirement to be fingerprinted before departure (and they only announced it in English, and the flight was going to Japan) - so I don't know if people will miss out and then have trouble coming back into the US at a later date.