They definitely have. I think it hurts the sport a little. Think about all the kids who grew up loving a player because of who he was to their team, to their city. It's too bad that things appear to be changing away from that. Kobe may have been the last player we had who was devoted to his team. I guess Lebron came back so there is something to be said about that.
Kids and one's status in life constantly changes, and I'm not one to hold a celebrity hostage by saying that they must make decisions based on the feelings of their fans. Playing sports is their occupation, and with any occupation, they have the right to choose to be employed elsewhere, especially when it's beneficial to them and their families. Nowadays, it's not uncommon for a 20 year old to have had 10 different jobs already.