We run an email spam filtering service. This service runs on 26 servers, 22 of which are on EC2.
I dont see a time when we will be serverless...we actually plan to run 70% of or traffic through our own servers...this will give us redundancy...we plan to use AWS to give us scalability and the burstable capacity that we need.
We are using AWS to help us to setup our business model and prove our technology is scalable. EC2 allows us to compete with our large VC funded competitors....AWS rocks!