False. Why would they want to turn gold into shit, literally?
This assumes that a large node wants to support the bitcoin network.
Let us consider if a node wants to undermine bitcoin by showing (very publicly) a few large double-spends?
What would happen to the value of the blockchain? What would it do in terms of trust?
Would any serious players ever touch bitcoin again?
So no, we shouldn't need to trust a third party for anything. After all, that's the whole point to bitcoin in the first place!
We need to question trust. ALL THE TIME. If bitcoin requires trust, then it is broken.
For a possible solution, check this thread:
http://forum.bitcoin.org/index.php?topic=9137.0