What if someone invents a way to automate microtransaction floods that come from a random source each time? that would be an headache.
Exactly, there are many ways to spam the network, so there is no universal solutions, each type of spam can be identified through a pattern, and blocked through a protocol change, like anti virus /malware software update
Because majority of bitcoins are hoarded and used for large transactions, the spam will not impact too much, it will just reduce people's transaction frequency and increase the transacted amount each time (thus more fee is bearable). Only exchanges who do frequent transactions will be affected
At 7tps spam rate, 600K transactions per day will cost 60 btc at a fee of 0.0001 btc, that is $18000 at exchange rate of $300. even if the fee rise to 0.001 btc and blocksize increase to 10MB to make 70tps possible, that is $1.8 million, pocket change for banks. So if banks want to disable bitcoin, they can do it easily for a sustained period of time (FED can print 2.8 billion per day in QE). However, if bitcoin price rise another 10 times, fee rise to 0.01 btc and blocksize increase to 100MB, then banks need 1.8 billion per day to disable bitcoin, not practical any more, but then transaction will cost $30, just like an international wire, not suitable for small transactions any more
