Why does Odysseus make sure that Polyphemus knows his name?

The curse that Polyphemus casts down upon Odysseus as he leaves the Cyclopes' Island is an event around which the entire plot of the Odyssey hinges. However, Polyphemus is only able to inflict this vengeful curse because he knows Odysseus' true name. From the modern reader's perspective, Odysseus' actions seem completely baffling. He reveals his name as his crew is already beginning to sail away without any apparent incentive. However, Odysseus' need to make sure that Polyphemus knows his name derives from the traditional Ancient Greek notion of 'kleos' or 'glory'.
For the Homeric heroes of the Iliad, fame and glory are the primary motivations for almost every character (with Hector being a notable exception). These heroes believed that true immortality could only be achieved by attaining immortal fame through heroic deeds. In this context, Odysseus' actions begin to make sense, for although he has already blinded and outwitted Polyphemus, he has done so as 'Nobody' ('oudeis'). Thus, Odysseus cannot claim Nobody's kleos for defeating the cyclops unless he reveals his true name. However, while Odysseus succeeds in claiming his rightful glory, by doing so he simultaneously condemns every sailor aboard his ship and himself to ten years of wandering. It is in this way that Homer highlights how the heroic code of wartime adhered to in the Iliad may no longer be applicable in the new, peacetime world explored by the Odyssey.

Odysseus has just outsmarted the Cyclops Polyphemus. He's blinded the hideous giant with a sharpened stake and while Polyphemus was screaming and flailing about in agony, Odysseus and his remaining crew-mates managed to escape by clinging to the bellies of sheep.
But this isn't enough for Odysseus; he has to rub Polyphemus's nose right in it. As he and his men are about to set sail Odysseus foolishly taunts the Cyclops, revealing his identity. Odysseus is full of bravado, and the adrenaline is coursing through his veins. He and his men had been trapped inside the Cyclops' cave for several days, where Polyphemus snacked on some of the ship's crew. So we can perhaps forgive Odysseus for his over-exuberance. He's glad to be alive, and even more glad that he was able to outsmart the Cyclops.
Prior to the departure of Odysseus and his men, Polyphemus had thought that Odysseus's name was "nobody." So when he screams that "nobody" has blinded him, the other giants on the island don't think there's anything wrong. But now, thanks to Odysseus, he knows his real name, and prays to his father Poseidon, the god of the sea, to exact a terrible revenge on the man who blinded him.