The gift: some players just have it, not through superior skill or athletic ability but through some intangible gift that they bring with them from team to team. They create chemistry and make their teams better. James Posey is a classic example of this type.
The curse: some players carry it everywhere they go. No matter how talented, how superior their athletic ability they are a drag on their team. Something about them spreads dysfunction. Stephon Marbury is such a player, every team he leaves gets better.
If last years signing of James Posey was a brilliant move that helped glue this team of stars together, then signing Marbury may go down as the opposite. A move that prematurely dismantles this team from the inside.