My concern isn't with individual bitcoin users but governments, what if a government spammed the network with say $1 Billion dollars worth of tiny dust transactions, including fees? The backlog of unconfirmed transactions would seem to effectively render the blockchain useless at that point and people would no longer have trust in or want to wait for transactions to confirm. This seems like it could be a major issue for the protocol...are their any defenses in place currently for some type of attack like this?
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.
Miners can also choose to not confirm these dust transactions, esepcially since they opt to choose the highest transactions first.