Amazon just announced "[Spot Instances](http://aws.amazon.com/ec2/spot-instances/)" for their EC2 based infrastructure. I was wondering what sort of workloads would be appropriate for such service?

> 
> Spot Instances enable you to bid for
>  unused Amazon EC2 capacity. Instances
>  are charged the Spot Price set by
>  Amazon EC2, which fluctuates
>  periodically depending on the supply
>  of and demand for Spot Instance
>  capacity.
> 
> 
> 

[Interesting quote](http://www.elasticvapor.com/2009/12/spot-on-amazon-commoditizes-cloud.html): 

> 
> The philosophy of JIT is simple: inventory is waste.
> 
> 
> 

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EDITED:

I wonder if there are applications that could sustain themselves (read: be viable) just by leveraging a large volume of those Spot instances. Think about it: imagine you get 10 instances for the price of 1 on average... of course there wouldn't be guarantees but in the case that no Spot instances are available, a number of "normal" instances could be kicked-of.