The RCP article on United was interesting...though it brings out a more blunt point, namely "When should one party in a dispute not have the ability to resort to force in order to breach?"
I threw a bit more thought into the "When would I take a 24-hour delay?" question:
-If I don't have a must-attend function in that timeframe/wouldn't inconvenience me and I won't incur losses as a result (e.g. a non-refundable cancelled-out hotel room), my point is probably $250-500 in cash or about a $1000-2000 voucher. The latter depends on my likelihood/willingness to fly the airline again: I'd happily take a $500 voucher from VX (on DL I'd probably hold out for $750-1000) where on UA, VS, or VA I'd require enough money to reliably be able to book a significant one-way trip on them in a premium cabin.
--Modifying this is where I am. If I'm in Chicago, for example, I have friends I can then grab dinner with. Ditto Seattle, and in Orlando I can add "visit Disney" with one of those friends. If I'm in Minneapolis or Houston, not so much.
--Also, depending on where I am/where I'm going I might instead opt for a cancellation if I can make a train work instead. If I'm coming home via New York and this happens in an NYC airport, presuming space availability I can almost always beat a 24-hour delay on Amtrak. If I'm coming home from Florida, it's not too far behind.
-Ok, let's say I have a "must-attend" function. For example, there are certain meetings that I'm in charge of running, but there are also times I'm hosting an event and my absence would be *ahem* bad form. At this point, my price has just gone up dramatically since you're also paying for me to be embarrassed at missing what amounts to a job function. Throw $1000-1500 cash at me (again, there's wiggle room based on where I am) or the voucher starts getting expensive (at this point you'd better be ready to fly me somewhere very nice in J/F for next to nothing).
-And then there are circumstances where I would not accept a voucher or cash, full stop, for this sort of delay. Weddings, funerals, seeing friends and family one last time before they go on a military deployment, or things that would result in me getting sacked from a job...these things exist and they're show-stoppers.