So, obviously, criminal-minded hackers are abusing the bitcoin economy by way of these DDoS manipulations, reaping profits for themselves while bringing down exchanges, market viability, public perception. Like gangsters they only care about enriching themselves and give no thought to running their victims into extinction in the process. Nothing new here, crooks is crooks, but this is my thought...
The hackers seem to be attacking the exchanges separately, targeting them at random times. Each exchange seems small enough to be vulnerable, yet the the entire bitcoin economy would be too large to effectively manipulate as a whole (unless they keep running it down like recently, then eventually even its entirety will be diminished to an easily manipulated size) Conversely, no one wants to see a single centralized exchange, and the idea of a decentralized p2p exchange is ... I don't know enough about this to know if it is even possible? BUT... here's an idea, maybe I'm missing something (or many things), but what if the separate exchanges entered into a sort of agreement... like they could pass the traffic from one to the other, when under attack, and keep the trade moving despite all these random attacks. The idea of a safety valve/co-operative agreement whereby exchanges A, B, C and D agree to carry the locked out volume for each other whilst any one of them are being targeted. i.e. MtGox is getting DDoS hard, so they pass all traffic to the other exchanges, and vice versa. I know this might seem far-fetched, like why would they give business to their competition, and all users would need to be registered with every exchange, not everybody trusts every exchange (or any for that matter). There would have to be a huge leap of faith, and some sort of unifying bond or agreement. I don't know how it would look if it did exist exactly, but the idea of forcing the hackers to have to spread their resources so thin seems like a ok idea to my n00b brain. These gangsters are just going to get richer and stronger, and they will steal everything until nothing is left.
So I guess the TL;DR is "united the exchanges will stand, divided they will fall."
Maybe I'm hopelessly naive, maybe this resembles the "central Bank Authority" too much, IDK! Go ahead and have at me. We need to do something because every attack seems to come with the reply from the exchanges of "we have got it all under control and are working to make everything more secure" then 12 hrs later BOOM! Another DDoS and some Russian Mobster gets that much more millions of dollars to launch that much huger a DDoS next time (like a few hours from now)
I might be shooting from the hip here but it seems like as long as all the major exchanges make themselves "gateways" what you describe and desire is called Ripple. Am I Right? Note: I'm not particularly wedded to the idea of Ripple, it just seems like what you describe fits that bill.