Amazon EC2

EC2 is only interesting if we need to raise a lot of similar servers, or to vary their number depending on the load. For a single server, though a little expensive. And small instances are not very nimble. Similar in performance and quality will obviously be cheaper VPS (I recommend linode)

Feature of EC2 is that the other Amazon services such as S3, SimpleDB, Simple Queue, etc. will work faster. If you store data in the SDB, the files in S3, messages in SQS, then give/receive their best with the EC2 instance, because scaroth data exchange within an infrastructure Amazon is very high.
In General, EC2 is expensive, and its instances are not protected from falls. Thus irretrievably lost ALL data. Therefore, the use of EC2 add service use the virtual drive (mount), which will always be a backup on S3. Feel? One service leads to another. And you will have to choose whether to switch to amazonesque the cloud completely or to look for alternatives.
As has been written above, I would recommend linode.

EC2 is convenient when you want to start a big project. Pre-configured servers are started for a couple of minutes.
There is also a functional shell RightScale that enables you to logically group servers, assign roles, create templates and bind the boot-scripts to each server. There is also the possibility to do autoscaling in a short time. Depending on the load will automatically start a new server.
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If you need to run a couple of servers, rackspace.com your case.
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There will be questions on the topic — a personal contact.

Think about it. But if a small ddos?
You pay for the channel and the volume and load for the full program.
I, as an experiment, I made some Debian shook looked and realized that it is not clear why it can be used so that it was not very expensive, and sometimes without ddos protest will hang and will eat your money.