Contrary to popular belief, even trotted out here on HN in about half our discussions on BitCoin, currencies are not just something that some government said somewhere is worth whatever. They need to back to something. US currency backs to the fact that the US law enforcement and potentially military (if you're big enough) will come after you if you fail to pay taxes, which, while perhaps a bit brutalist and in violation of some of our more delicate follow-citizen's tastes, turns out to be enough to keep an economy humming along.
If the Venezuelan government is incompetent enough to have that same delusional view of how currency valuation works... well... behold its results.