Is cloud storage the factor that is driving companies to AWS? I'm sure that's huge for NetFlix, but they are an outlier. My bet would be on EC2 usage as being a better growth metric.
Well, to pick a high-profile AWS-user here: all of Dropbox runs on S3, and apparently a bit of EC2, last I saw. Not that I think they account for a truly significant amount of Amazon's traffic, but they're not small-time either.