I've run TweetStats on EC2 for the past year using the great scalr.net to provision new instances. It's expensive as heck (the smallest instance scalr allows i

I've run TweetStats on EC2 for the past year using the great scalr.net to provision new instances. It's expensive as heck (the smallest instance scalr allows is an EC2 large), but it works great. Scalr monitors one of several stats you can specify (RAM, CPU, queue size, HTTP response) and will spin up instances (you can specify a max) as necessary. Granted the app has to be built to support such multiple app servers, which may be easier in some cases than others. Sounds like the cloud server was rather inconvenient, couldn't handle immediate load, and required your manual intervention. Always tough to predict traffic spikes from Twitter. ;)