With 1MB blocks such projects are actually quite reasonable. Data rates in the 2-3KB/second are required to keep up with the network, and for miners, bursts of 10 to 100x that to keep the orphan rate low. Amateurs with off-the-shelf systems can build the hardware links those decentralized networks run on - one example is the
RONJA project. Essentially the basic information needed to validate and audit the blockchain would be broadcast to everyone, and then either on-chain transactions, or off-chain transaction systems audited with blockchain information can be used to actually transfer funds.
Bitcoin is especially suited to decentralized networks because it doesn't need routing. Every peer passes every valid message it sees, either a block or a transaction, to all of it's peers, so you don't need complex routing algorithms to determine where the data should go. The Bitcoincard project was interesting in that regard; it was claimed to have integrated point to point radio links in each card. While the project itself appears to be vaporware, the basic idea is possible.
