It's just me and Stephon
Now that that's out of the way (and if you really watched those 3 links, in the back of your head right now you're singing "It's just me and Stephon, it's just ME and Stephon..." Admit it, you are), let's talk about what it means on the court. Fantasy-wise, I don't expect it to really affect anyone...Stephon Marbury isn't displacing Rajon Rondo in the starting unit, and none of the reserves are really fantasy-worthy.
For the Celtics themselves, it appears to be a moderate risk/reasonable reward proposition. As a Celtics fan that has closely followed Marbury's career, I was hesitant to embrace a Marbury signing...just too much baggage there. On the other hand, Steph really does have the ability to be a great boon to the team. He is all of the ball-handler under pressure that neither Eddie House nor Sam Cassell were last season, he can definitely provide enough offense to the second unit for it to get by even while Garnett/Pierce/Allen rest, and he has in the past shown that he can personally make hustle/role player big men into offensive threats using the drive and kick (could be great for Leon Powe, Mikki Moore and Big Baby Davis). Assuming he keeps his head on straight and hasn't lost all of his skill, it should work well for the Celtics. And if he can't keep it together, presumably the Celtics could just bury/cut him and move on. But at the very least, Marbury should help keep things interesting.
(It's just me and Stephon, it's just ME and Stephon...)