I've been disappointed that I didn't grok why you couldn't use entanglement to make an ansible, so I asked around on the Viable Paradise Yahoo! Group, and got some insight. Thanks to Laura, Meredith, Calvin, and Leo.
Here's what I've got in my head:
In order to transmit information, one party must set (that is, determine) a property of the universe, and another must read (that is, measure) that same property. When each party is in possession of one particle of an entangled pair, neither party can set any entangled state of the particles (like, say, spin). One party (A) can set the property whether-the-waveform-has-collapsed-yet, by reading any of the entangled states, but the other party (B) can't read that same collapsed-yet property; B can only read the entangled state, which is something A didn't set. So even though the two particles might be said to be communicating with each other instantaneously, the two people who have them can't.
I'm not sure if I've got it right, but it feels good to think that I grok it.