Where is all the efficiency with this free seating idea?
You check-in and instead of getting a boarding pass with a seat, you get a boarding pass with a sequence number. No saving there.
At the gate, the staff would have to be very vigilant to ensure your boarding sequence pass is valid for the flight and you are not boarding out of sequence to avoid a sh@t fight onboard. A card reader would be faster, error proof, more secure and the F/A's wouldn't have to move people about to ensure trim.
There may be savings for a start up with the technology investment, but when you can nick it off big brother, where's the saving?
DJ are already highlighting seat allocation in their ads.
I suspect this idea will be among the first changes to the business model that will blow the budget with the reinvestment costs.