IANAeconomist, but a currency is back by trade. You and I accept a dollar or a gold coin because other people accept them at (usually) parity for value-- call it a network effect.
But, a dollar or a gold coin has limited value if you can't trade it. The same for a bitcoin; except, it can only be traded via coordination with many other actors in the economy. (The longest block chain is the "truth.") While a dollar or a gold coin can be traded physically, a bitcoin is never traded until the economy as a whole agrees-- the record of the transaction appears in the chain.
Therefore, the act of trading bitcoins, and by extension bitcoin itself, is backed by the presumption that Internet access will be pervasive and unfiltered.
But, a dollar or a gold coin has limited value if you can't trade it. The same for a bitcoin; except, it can only be traded via coordination with many other actors in the economy. (The longest block chain is the "truth.") While a dollar or a gold coin can be traded physically, a bitcoin is never traded until the economy as a whole agrees-- the record of the transaction appears in the chain.
Therefore, the act of trading bitcoins, and by extension bitcoin itself, is backed by the presumption that Internet access will be pervasive and unfiltered.