This last is typical of regional airlines boarding several flights at once. I've seen it happen at my home airport. The more on-the-ball GAs and FAs make repeated announcements as to where this particular flight is headed. I've seen folks get up and leave the plane in a panic when they heard where the flight was going. At least the announcements seem to help. If none is made, I can see lots of folks winding up in the wrong place. Purely the airline's fault in this case. All the planes look the same, all are lined up on the ramp and all are boarding at the same time. Recipe for a screw-up.