bitcoin dust spamming - could the blockchain be rendered useless?
Perhaps only for other dust sized transactions with minimal fees. Dust transactions with small fees are low priority and are NOT guaranteed to be confirmed in the order the transaction was placed but rather by the priority. So lets say there is a backlog of 1 million dust transactions, I could create a transaction using 1 output for 0.01 and include a fee of 0.0002 and it should be included in the next few blocks, well before any of those 1 million dust transactions.