Why can't two candidates initiate a debate between each other (say Romney suggesting a debate to Giuliani) in the same manner that Lincoln and Douglas exchanged letters agreeing to the terms, times, and locations for their debates?  I realize that they could not cause radio/TV stations to cover it live, but they could certainly stream it to the internet and post it online at very little cost -- and in all likelihood, broadcast news would show some extracts.  What's preventing this?  Why doesn't this happen?

It would certainly be far more informative than a CNN/YouTube circus... and more informative than the sound-bite Q&A with eight candidates on a stage