I guess my question would be twofold: (1) Are the musicians being replaced with MIDI-equipped machines and/or pre-recorded tracks because of costs, lack of funding, etc? or; (2) Are the musicians being replaced with MIDI-equipped machines and/or pre-recorded tracks due to the lack of qualified, experienced musicians... Oh well, I guess the second question is somewhat ridiculous...but I always try to play devil's advocate....
Anyway, getting to the matter at hand. I would venture to say that Broadway producers are responding to the economy and the recession. It probably costs far less to use pre-recorded tracks than live musicians. However, the musicians unions probably need to protest against this... I'm sure they are not happy that this "cost cutting effort" is cutting into their paychecks.
In my opinion, there is nothing like a truely "live" performance. There can be digital enhancements here and there; but to completely eliminate a live orchestra and replace the music with an orchestrated track? I think not. What's next, replacing the actors with holograms? LOL! Then essentially you just have a film; nothing live.