I'll add that the biggest value proposition for the Raiden Network is not that light client users will require RDN to pay for services provided by full node operators, but that the Raiden Network is a faster, cheaper, broader and unifying second layer for transacting across all ERC20-based (and potentially more) blockchains. If the Raiden Network is successful, RDN is poised to become the base token for value transfer across the entire crypto ecosystem.
RE: What is Raiden? (RDN) - Raiden Network