Stumpled across this one. I like the way it illustrates what is already being said a lot on the forum.
If you know how he does it, dont ruin it for those who dont 
The rest of the episode is out there, i'm sure you know where to look.
how did he do it?
I saw the whole 1 hour , about the house racing bets, it was pretty interesting hour.
<spoiler>
I figured out that without using any tricks he must've flipped the coin till he got his result..but come on, who would be so mad to do that..must be something else...WRONG
So I watched the full video. He drugs the horses or he contacted 10^4 people (I thought there were 10 horses in a race). Impossible! Too much work, it's easier to drug or fix the race lol....WRONG
But I'm sure he didn't use 1 million groups of reporters for the photo trick...or did he
</spoiler>
What I've personally learned:
1. Sometimes it seems impossible to achieve something even though you know how to do it, only because your brain rejects the method since it involves too much work and it thinks it's not worth it. (But I'm sure Derren made more money than he had to pay for the bets and the crew that helped with the system)
2. You sometimes need an army (outsourcing babe!) to delegate work to and make the system work.
For this who want to see the explanation video
https://www.youtube.com/watch?v=n1SJ-Tn3bcQ
One word:
Statistics.