Andy... what is happening between Midwest/Republic is nothing new, therefore nobody should be surprised, except the tables are turned. Every regional has been apart of some sort of growth at some other airlines expense, as has mainline. It's called the airline business and has a fancy name for it... whipsaw.
The big difference at the regional level is that none of these regional airlines actually own any of their flying. It is all flying that is owned by mainline that is allocated to whatever operator the mainline mgmt wants. Pinnacle is not stealing Comair flying, they're just taking over flying traditionally flown by Comair or other DL connection partners. Same stuff at NWA, AA, CO, US etc...