Why does Shiva have a 'Neela kantha'-blue throat?

Last Shivaratri Sri Swami Vishwananda explained why Shiva is also called 'Neela Kantha'- the One with the blue throat.

Sri Swami Vishwananda: Today is that He drank the poison.
Do you know the story of the churning of the Ocean? (Some say yes)
When the Devas and the demons churned the Ocean to get the amrit, what came out first was… (Some say poison) Poison.
This poison would eliminate everything, would destroy everything, so the Gods appeared to Shiva.
Of course He could have said ‘no’.
He could have said “Okay, bye; no need to save these humans.” (Smiling)
But to show how much He loves everybody, He accepted to swallow the poison and kept it in His throat.
That’s why He is called “Neela kantha”- the blue throat.
And this is the day, when this happened.


Here is another source about how Shiva got the blue throat:
http://library.thinkquest.org/C0118142/orient/shiva.php

And here another very good explanation of how Shivajis neck turned blue (nice video):
http://www.youtube.com/watch?v=AD8zODCUofA