Otherwise, maybe it's the new type of flood attack, cost-of-service (CoS), applicable against those who use ‘invincible’ cloud infrastructure such as Amazon's.
Cost-of-service-attack: Consuming bandwidth or other resources in cloud based solutions to drive up the cost of running the service.
Very easy when the cost is so tightly coupled with the resource use...
I dunno though, it's all technically bandwidth flood in the end. The consequences (or goals) of flood may include immediate or eventual denial of service, high cost of service, various security attacks, or probably all at once—further classification surely is complicated.
Meanwhile, both terms DoS and CoS are a bit vague, too. Say, turning off a server or forcing providers to alter their DNS records more or less qualifies as denial of service attack (which, by Wikipedia's definition, is “an attempt to make a computer or network resource unavailable to its intended users”).
Aanyway.. You're right, it boils down to bandwidth flood (or maybe CPU..) in the end.
Maybe CoS is not really a technical term, just made more relevant by the technological changes. OP would have been charged much less had he not been using "the cloud".
Lets say I have small'ish competitor hosting their app on EC2. Using classical DoS techniques, how much can I ramp up their bill before they notice? Or can actually stop it? What if I run it on a smaller scale, "just" doubling their bandwidth bill.. Will they notice? Maybe they'll believe it's extra users ;)
If it requires a lot of effort to productize, Amazon could potentially offer it as a service $0.5/hr to ensure you are not making major goof ups.
This is why most cloud services have a customisable limit on how many virtual servers can be booted automatically, a solution is yet to be found for protecting S3.
"[snip]..one might envision that instead of worrying about a lack of resources, the elasticity of the cloud could actually provide a surplus of compute, network and storage utility that could be just as bad as a deficit"
http://rationalsecurity.typepad.com/blog/2009/01/a-couple-of...
In any case, it may not be a denial-of-service, but if you can find someone with an S3 bucket with large files you could maliciously cause them to rack up a huge bandwidth bill using this mechanism. I guess you could say it's a DDOM (Distributed Denial of Money).