[splat]

No data is ever transmitted via quantum entanglement (at least, data from the perspective of the observer). Entanglement is simply when two particles exist in the same quantum state. (Or, to be more precise, in the same superposition of quantum states.) When the state is observed (say, an experimenter examines one of the particles), then the entire wavefunction collapses to a single quantum state. The two particles in the system therefore collapse to the same state instantaneously, but no information can ever be transmitted in this way.

[larsendt]

Erm. Isn't it possible to transmit data that way, specifically by affecting the state of one particle, and observing the other?

[Ralith]

"Observing" is another way of saying "affecting the state of."