It was taken from the 'exit polls', probably.
As it turns out, California had a ~2/3 majority for Obama. And with 55 EV (is any state higher?), that pretty much gave it to Obama. Hawaii was even higher, at 75%.
(I find it rather funny that a few 'key' states are mentioned, but CA is left out - even though CA has the most EV.)
If the actual count refutes the projected count, you can be sure that it will be noticed.
But, ya, I know what you mean. I live in CA. It was a couple seconds before 8PM here (poll closing time) when the banners went up for Obama.
Personally, I think it was a setup from the beginning. McCain's concession speech was his best moment of his entire campaign. It seems like he was just itching to lose, from beginning to end. He seemed dumb and stupid, until that eloquent moment.
Obama is the 'pretty boy'. And, he took it as such. Let's see what he does with it, now that he has it.
And personally, I consider him as the single most greatest danger in this world. By comparison, I would put him (with world leaders) as to Creflo Dollar or T.D. Jakes (is with Christianity).