Excellent topic, and great analysis of the moral and purposeful aspects of the carpool lane.
I would like to add another point of practicality to the discussion, that carpool lanes are highly unsafe. Typically on a multilane road the middle lane is the safest because it is not merging with traffic coming on and off the roadway, nor is it where the fastest traffic piles up, nor is it up against any concrete barrier or small shoulder that a vehicle could not typically fit into. In the middle lanes you have less surprises and some room to maneuver when you need it. Carpool lanes change this dynamic and bring cars across the roadway based on their occupancy. Therefore, carpool lanes change the dynamic of the highway merging and speed ratios, making 3 lanes cautious instead of the typical 2.
The difference in speeds between the carpool lane and the adjacent open lane can be dramatic, at times leaving HOV drivers pinned between a concrete barrier on their left and a wall of cars on their right with nowhere to maneuver. Add to that the car riding your tail at 70MPH expecting you to speed up, and you're now in perilous situation that is not easy to get out of. I can tell that authorities added the solid lines between exits to help separate the carpool lane from the adjacent open lane. That does little good when somebody is riding your tail, or something else goes wrong and you need to exit as soon as possible.
The affect this realization has one me is I never take the carpool lane, regardless of the occupancy of my vehicle. I recommend others avoid them as well.
Let's please remove carpool lanes and return them to normal traffic. The crazies wishing to speed beyond belief can use that lane and the remaining lanes can accommodate the sane people!
One more thought regarding the moral and purposeful aspects of the carpool lane. If we were serious about carpooling, we'd be serious about public transportation, in particular rapid transportation and commute corridors. If we cannot afford to build transit tunnels or platforms, I believe we can re-purpose highway lanes for dedicated bus or train services. Since in the USA we built freeways and tollways as our primary infrastructure, I see no moral problem re-purposing that infrastructure with something of greater public and environmental value that is safe (in fact much safer) to use.
If I'm really dreaming, I'd like to see a train that vehicles can load and unload to/from at stations. Think about it. If you could board your car onto a train as you would a ferry, but instead of riding across water cruise through a commute corridor, you could really get around with ease! We desperately need that between Los Angeles and San Francisco.
Thanks for covering this important topic, and I do hope to see positive changes someday.