Wow. This is truely bad if it becomes policy, though I can't believe it would do. Firstly, as the OP says, removing I94-W's from passports takes around 2 seconds, especially as it's usually done at checkin and the thing is stapled to the boarding pass in any case. Secondly, what about those with white I94's? These should also be surrendered at this time if the flight is outside of North America. Any non-resident who is not a citizen of a visa-waiver country will have one. Thirdly, I94-W's can be returned to embassies in your home country if you forget to surrender one, so it's not exactly the end of the word if you do.

I'd be very surprised if this becomes widespread, but I guess anything goes in the name of "security".