Eh I don't know.
It's tough to say LeBron made a mistake, yet. Even if the Heat don't win it all this year or next. Look it took this way, it wasn't until Shaq's 4th season in LA that they won it all, then he won 3 straight and 4 overall. People don't think about those first 3 Laker seasons when thinking of Shaq's legacy now.
Carmelo Anthony definitely made the wrong move, but that's because he didn't make a basketball decision. He wanted to live in New York, and his ego thought he was good enough to win anywhere. He didn't consider coaching style, teammates, etc. Dwight is the same way, he's not making a basketball decision. If it wasn't obvious from the start, it should have been obvious when he said he didn't want to play in Chicago. These guys take winning for granted. They can win with any 11 guys, just not the 11 guys on their current team.
Chris Paul is way better off in LA, definitely a good move for him. Barring some unforseen circumstance (major injury to him or Blake), they'll be contenders for a while.
And how can Bosh even be mentioned? He could put up good stats and hope to make the playoffs, or slightly worse numbers and be on a good team. No matter what happens to him in Miami, he's better off than he would have been in Toronto.
And then he goes on to mentioned guys like McGrady, Vince Carter, and Shawn Marion, really? They would have been better off staying with their current teams? Marion has a ring, and Carter and McGrady wouldn't have won anything in Toronto anyways.
Sure forcing a trade or leaving via free agency rarely works out, but know what else rarely works out staying with the team that drafted you and re-signing with whatever team you happen to be on.
Assume 450 players in the NBA, and only 15 win a ring every year. So no matter what you do, it doesn't work out for 97% of the players in the NBA.