This is the thing with CDNs... why does one going down cause an outage, and not a slowdown? The whole point of a CDN (content delivery network) is to cache frequently accessed content physically nearer the viewer, to reduce load times. The actual source data still exists on the source servers back at the host... the CDN is just carrying a COPY of the data. So when the CDN goes down, why doesn't the system just failover to the original (albeit slower) servers, instead of 404ing everything? Is this just sloppy coding on the host's side of things? Are the CDN's being too heavily leveraged as the ONLY data source...?
Same reason a power station going down causes a blackout. Cascades. Buddy of mine took down Netflix for 36 hours by going with BrandX to host Moesha for theWB.com. BrandX had determined that TheWB.com's streaming needs were modest and that they could provide a better deal than Akamai. BrandX had made this determination, however, by looking at TheWB's aggregate weekly data, not their aggregate hourly data, so they missed the fact that 80% of TheWB's weekly traffic occurred in the three hours after Moesha aired. Thus did their CDN experience 800% of their estimated traffic, thus did it crash, thus did the entire CDN failover to Akamai, which had allocated failover due to BrandX's estimates, not TheWB's realities, thus did Netflix, much of Amazon and half of Youtube eat shit. Now granted - that was 2006 (it wasn't Moesha, but something similar). Things are hopefully better. But there's still thunderous amounts of incompetence in places you would have expected it to die out.