What will EC2 be used for?

Update (9/6): I received another email informing me of more signups available (in my inbox at 2AM PT), but by the time I clicked on the link this morning I was too late. According to the email:

If you are unable to sign up in this round, we encourage you to stay ready. We intend on activating more beta users in the coming weeks.

Last week, I received an email from Amazon announcing a new beta web service named, "Amazon Elastic Computing Cloud", or EC2 for short. I had messed around with s3 before so I was given the opportunity to preview EC2. By the time I signed in, I was notified that,

The Amazon EC2 Limited Beta is Currently Full
We will e-mail you when we can accommodate additional users.

Ah well, I probably wouldn't have done anything with it anyway.

But this sounds really cool! One of the first things that came to mind is the power of distributed computing for short periods of time. Firing up a reliable web server is one thing, but this seems like it will really lower the barrier to using many machines at once; you don't have to own them, you just pay to use them for a little while then kill the jobs.

For instance, imagine firing up 100 instances of a linux box loaded up with a python script to vote for your story on digg and reddit, bringing you to the front page, and sidestepping whatever security they probably have in place to restrict multiple votes coming from a single IP address. As soon as the deed was done, you could halt the processes as well as the running tab. At $0.10 per instance hour, that might only cost you ten bucks!

It also reminds me of the command and control style bot networks used by spammers and denial of service attackers. The process of gaining control of people's computers via viruses seems like a pain in the neck compared to the ease of spawning the exact machine images you desire via EC2.

I'm sure Amazon has thought of the security implications, and the fact that you have to register with a credit card before using any of their chargeable web services would make it much tougher. Plus, they already mention, "If you wish to run more than 20 instances, please contact us at aws@amazon.com."

No matter the case, I look forward to see what comes of EC2, and eventually playing around with it.