Cloudy Days

It seems that cloud computing is the new SOA, but looking around at the current offerings, it feels like we are definitely in the 'kick the tires' stage.  I don't think the barriers are as much technological as they are logistical and organizational.  As mentioned in a recent InformationWeek article, Amazon can't even handle purchase orders in its EC2 business.  You can only pay for Amazon clouds with a credit card?  I guess Amazon still views buying cloud MIPS the same as buying a 'Marley and Me' DVD.
Yet, the pricing is compelling.  For $.80 an hour, you get a powerful Linux server with the following specs:

High-CPU Extra Large Instance
7 GB of memory
20 EC2 Compute Units (8 virtual cores with 2.5 EC2 Compute Units each)
1690 GB of instance storage
64-bit platform
I/O Performance: High
Price: $0.80 per instance hour

Imagine doing backtesting on an algorithm.  You provision 1000 servers for an hour for the price of $800.  Imagine the infrastructure you'd need to build out to be able to do this in-house.