Apparently, Sprint's not doing so well. Apparently they're having customer retention problems. That means that people would rather go to the hassle of changing phone service providers than continue giving their money to Sprint. While it wasn't my number one reason for switching, I can say from personal experience that Sprint's horrendous customer service was the thing that pushed me over the edge into iPhone-land and the loving arms of AT&T. AT&T might not be perfect, and I can understand why a lot of people are unhappy with them, but they still kick Sprint's ass when it comes to customer service.
I will never go back to Sprint; they have lost me forever as a customer. But if they want to hold onto the ones they have, one thing they might try, for starters, is not treating them like shit.
Just a thought.