There's experiments that provide evidence for pair-anti-pair annihilation within the vaccum of space, but it's too inefficient of a source to extract energy from. I think if there is "infinite" energy and we can just take whatever we want from it, there's going to need to be some more proof and equations other than just "well its probable isn't it?".
Also, virtual particles aren't real, but they aren't fake. They occupy a sort of "i" realm.