I have encountered a picture on 9gag, one of "weird facts" ones, that stated following:
Mythbusters once investigated the explosive properties of an easily available material. It was so explosive that they decided to destroy the footage. They contacted DARPA to warn them about how it could be used to make a homemade bomb.
Had this happened? And if it did, why DARPA and not something like Homeland Security? To my understanding, it's not DARPA function to protect from those who can create a bomb, and they already know how to create a bomb of their own.